Abstract: One of the major weather systems over the Tibetan Plateau is the Tibetan Plateau transverse shear line (TPTSL). Fourteen cases of TPTSLs that cause heavy rainfall and generated between June and August with a lifetime of 38 h were selected and composited using the ERA-5 reanalysis datasets provided by the European Centre for Medium-Range Weather Forecasts in order to reveal the effect of dynamic and thermodynamic forces on the intensity evolution of TPTSLs. The following are the results. (1) At 500 hPa, the TPTSL is generated in the saddle field between the Iran high and the western Pacific subtropical high, and it is located at the low-pressure center contoured by 584 dagpm and the warm center contoured by 272K, to the north of the specific humidity center. At 200 hPa, the TPTSL is located at the northern margin of the South Asian High and the south of the entrance region of the westerly jet stream. (2) The TPTSL intensity at 500 hPa exhibits a noticeable diurnal variation, with the highest intensity at 23 LT and the lowest at 13 LT (LT=UTC+6 h). (3) According to the vorticity budget, the divergence variation at the upper layers and the convergence at the lower layers over the Tibetan Plateau are indicative of the TPTSL intensity. The vorticity at 500 hPa reaches a maximum of 3 h later than that of the convergence. (4) As the TPTSL develops, the potential vorticity (PV) increases. According to the PV budget, water vapor and diabatic heating play important roles in TPTSL generation and evolution. The enhanced sensible heating results in an intensified ascent. When the water supply is sufficient, the latent heating is released, and the diabatic heating center rises to the middle layer, which is favorable for TPTSL generation and development.