A 3D thermo-elasto-hydrodynamic model is developed to analyze the sealing performance of a notchedmechanical seal applied in the reactor coolant pump. In the model, the generalized Reynolds equation,the energy equation coupled with notch heat balance equation, the heat conduction equations, and thedeformation equations of the sealing rings are iteratively solved by the finite element method. The filmpressure and temperature distribution are obtained, and the deformation of the sealing rings is revealedto study the mechanism of the notched mechanical seals. A parameterized study is conducted to analyzethe sealing performance under different operating conditions. As a comparison, the sealing performanceof non-notched seals is also studied. The results show that the hydrostatic effect is dominant in the loadcarrying capacity of the fluid film due to the radial mechanical and thermal deformations. The notch cancool the fluid film and influence the thermal deformation of seal rings. The sealing performance issensitive to the pressure difference, ambient temperature, and rotational speed. It is suggested to set thenotches on the softer sealing rings to acquire the greater hydrodynamic effect. Compared with the nonnotched, the notched end face holds a better lubrication performance, especially under lower rotationalspeed.