To analyze temperature rise influence by power plant thermal effluent， a 2-D hydrodynamic and thermal diffusional mathematical model was established based on previous work and with river regime-fitted computational meshes. Sensitivity analyses of parameters and coefficients in the thermal diffusion equation qualitatively show that this mathematical model can simulate the temperature rise influence. Application results also show that, the model has basically the same temperature-rise envelope in comparison with the physical model, and the simulation error of 1℃ envelope area between two models is within 8%.