The simulated results of regional climate model (RgrCM3) are sensitive to initial and lateral boundary conditions, model horizontal resolutions, and different parameterizations. The sensitivity experiments were conducted to improve the regional climate simulation over China with RgrCM3. The experiment results indicate that the regional climate simulation by using RegCM3 beginning from winter is suitable, as the results of simulation are not notably affected by initial bias. The improvement of the simulated results from the increase of horizontal resolution is indistinctive. Nest simulation with higher horizontal resolution is able to improve the simulated results. The exponential relaxation scheme and Grell convective precipitation parameterization are better than others in the regional climate simulation over China.