In 1950, Tsung-Dao Lee published his doctoral dissertation. The thesis made outstanding contributions to the calculation of hydrogen content in white dwarfs and the Chandrasekhar limit, proving that white dwarfs are the later stages of the evolution of stars with solar mass, making important contributions to the development of astrophysical evolution theory. The thesis also correctly presented the conductivity formula for very dense matter for the first time, which had been widely cited in materials science.

In 1951, Tsung-Dao Lee introduced Heisenberg's vortex-to-vortex energy transfer equation, demonstrating the differences between two-dimensional and three-dimensional fluid dynamics, and pointed out that two-dimensional fluids do not generate turbulence. This theory has made a significant contribution to the development of weather forecasting.

Before 1952, physicists had believed that the liquid phase could be obtained through analytical continuation of the gas phase, but this theory was found to have problems. In 1952, Tsung-Dao Lee collaborated with Chen-Ning Yang to obtain all different phases in a finite system by taking the limit of infinite volume. Subsequently, they used a specific lattice gas system as an example to perfectly illustrate the reliability of the conclusion, proposing the famous Lee-Yang single-circle theorem.

Between 1952 and 1953, Tsung-Dao Lee collaborated with D. Pines to study the interaction between electrons and lattice fields in polar crystals. In their research on the motion of slow electrons within polar crystals, they simplified polarons.  Their work  contributed to the formulation of BCS superconductivity theory in 1956.

In 1954, Tsung-Dao Lee published the famous "Lee model" theory in quantum field theory. In quantum field theory, most solutions are obtained through an approximate method, and their correctness needs to be tested. The Lee model has analytical solutions, which can be used to test the effectiveness of the approximate method. The establishment of this model has far-reaching significance for subsequent research in field theory and renormalization.

When several conservation laws are at work in the same system, it is often necessary to define new quantum numbers and new selection rules. In 1956, Tsung-Dao Lee and Chen-Ning Yang, while studying the mutual influence of strong isospin symmetry and charge conjugation C invariance, defined a new quantum number G, namely the G parity operator.

In 1956, he collaborated with Chen-Ning Yang to study the θ-τ puzzle, raised questions about parity conservation under weak interactions, made significant improvement to particle physics theory, and later won the 1957 Nobel Prize in Physics.

After proposing the non-conservation of parity (P) in 1956, Tsung-Dao Lee and Chen-Ning Yang found that the conservation of CPT and the non-conservation of P inevitably imply the non-conservation of CP. They immediately began their research, and their  results laid the theoretical foundation for the experiment of T and CP non-conservation in 1964 (which later won the 1980 Nobel Prize in Physics).

Tsung-Dao Lee conducted research on the many-body problem in quantum statistical mechanics. In the 1950s, there were two prominent research areas in the many-body problem: superconductivity and superfluidity. In 1959, Tsung-Dao Lee and Chen-Ning Yang collaborated to conduct a comprehensive analytical study of the low-temperature behavior of a dilute hard-sphere boson system, and made contributions to the study of superfluidity in helium II.

In 1957, Tsung-Dao Lee  collaborated with Chen-Ning Yang to propose the two-component neutrino theory. Starting from 1960, they also jointly analyzed the effects of high-energy neutrinos, suggesting directions for theoretical research and experimental work in this field for the next two decades.

In 1964, in collaboration with Nauenberg, Kinoshita proposed a method to eliminate mass singularities from observable quantities in processes involving particles with no (static) mass, thus resolving the difficulties arising from mass singularities when comparing theoretical results of quantum chromodynamics with experimental results. This work, also known as the KLN (Kinoshita-Lee-Nauenberg) theorem, is an indispensable theorem in current strong interaction experiments and serves as the theoretical basis for the discovery of quarks and gluons through high-energy jets.

After V. Fitch, J. Cronin and others discovered the violation of CP conservation, Tsung-Dao Lee proposed a model where T-violating is caused by spontaneous symmetry breaking.

In the 1970s and 1980s, Tsung-Dao Lee conducted a series of studies on the nature of the QCD vacuum. His new ideas charted a new fundamental research path for particle physicists engaged in strong interaction research. Lee and G.C. Wick discussed and established a bridge between the study of solitary particles and the study of vacuum properties, proposing the Lee-Wick nucleon excitation state, speculating on the possibility of a physical system that has not yet been observed, and promising a new fundamental research path for nuclear physics and the study of strong interactions of elementary particles.

In the 1970s, Tsung-Dao Lee pointed out that high-energy physics experiments had been striving to contain increasingly higher energies within increasingly smaller ranges. To study the vacuum, Tsung-Dao Lee argued that one must shift to another direction, that is,  containing very high energies within a considerably large range, and noted that a change in one of the masses would manifest as a transition from the usual nuclear matter to a new form of nuclear matter with higher density and binding energy, known as the "exotic" nuclear state.

Starting from 1976, Tsung-Dao Lee, R. Friedberg, and A. Sirlin discovered a batch of classical solutions and their quantum mechanical counterparts in field theory, which Tsung-Dao Lee referred to as non-topological solitons, and which led to  new research  in field theory. In 1978, they established a soliton model for strongons with R. Friedberg.

In 1982, to address the two major issues in lattice gauge theory: the doubling of fermion spectra and the violation of translational and rotational symmetries, Tsung-Dao Lee proposed the random lattice theory together with N. H. Christ and R. Friedberg.

In order to detect the "anomalous" nuclear state, Tsung-Dao Lee proposed the possibility of its production in relativistic heavy ion collisions, and thus established the field of relativistic heavy ion collisions.

Through a series of studies, Tsung-Dao Lee proposed that under certain conditions, black holes may not always emit blackbody radiation.

Tsung-Dao Lee had always dedicated himself to studying the fundamental laws of physics. For a long time, physicists had believed that continuous models were more fundamental, and discrete states (represented mathematically as difference equations) were approximations of continuous models. In the 1980s, Tsung-Dao Lee pointed out that discrete models are the more fundamental models in physics, and continuous models are approximations of discrete models.

In 1986, Tsung-Dao Lee applied the concept of non-topological solitons to stellar objects during his research on black hole issues. Taking into account the effects of general relativity, he founded the field of soliton star research. The existence of soliton star solutions opened up new possibilities of constructing cosmological and astronomical models.

Although there is no "matter" in a physical vacuum, due to the uncertainty principle, the existence of interactions inevitably causes energy fluctuations in the vacuum, thus making it a complex system. Tsung-Dao Lee concluded that a vacuum might be a physical medium exhibiting asymmetry, and that it is possible to generate new physical phenomena by altering the properties of a local vacuum.

To study the degenerate physical vacuum, it is necessary to solve the non-perturbative problem. Tsung-Dao Lee developed a new iterative method to solve the Schrödinger equation. By addressing the convergence issues surrounding the expansion, he pioneered a new direction in this field of research.

Tsung-Dao Lee introduced a phase factor that destroys the conservation of time reversal, establishing a direct connection between the neutrino mapping matrix and the CKM matrix of quarks, as well as the masses of light leptons and quarks.

Tsung-Dao Lee proposed the concept and model of "Timeon". He coined the name "Timeon" was  explaining, "The 'on' is derived from Confucius and Laozi. If this theory proves to be correct, Timeon will be a very special particle closely related to the existence of 'time'." In this theory, the existence of Timeon determines the distinction between the future and the past. How can the future and the past be distinguished? Everyone knows that time does not go backwards, but why can't it go backwards? The Timeon theory  explores this very basic question. However, how can this theory be proven? He pointed to the paper and said, "This paper analyzes what kind of experiments can help verify the measurement of 'time'. This is also closely related to the Daya Bay Neutrino Experiment."