Abstract: Solar radiation is obviously an important surface forcing factor. Currently short wave radiation scheme in GRAPES ( Global/ Regional Assimilation and Prediction System) is based on Dudhia (1989) and taken from MM5. It is a simple downward integration of solar flux, accounting for clear-air scattering (Lacis and Hansen 1974), water vapor absorption , cloud albedo and absorption, and uses look-up tables for clouds from Stephens (1978). Short wave radiation at the ground surface (GSW) is originally calculated under the assumption of horizontal surface. This method of estimating the GSW may lead to considerable errors when the model resolution becomes high and the model terrain steep. To improve solar short wave radiation parameterization, slope irradiance has been implemented into nonhydrostatic mesoscale model GRAPES as it has been used in many climate models for its good performance. In this paper, the effects of the slope irradiance on different short range weather processes in China under different model resolutions are simulated and discussed. In the simulation, topography heights are taken from NCEP with a resolution of 1 km, and the slope and orientation of terrain calculated by using the staggered difference schemes. The results show that when the model resolution is low and the slope of terrain is small, then the influence of slope and orientation of terrain on the GSW is negligible, otherwise, it is not negligible. Under the circumstance of the high resolution (3 and 6 km, hereafter the same), the increase or decrease of simulated precipitation are respectively corresponding to the decrease and increase of the GSW induced by the slope effect, the increments of precipitation are usually ranged between 5 and –5 mm. And furthermore, the surface temperature and heat fluxes are close correlated each other, mostly in the complex terrain mountainous regions. The changes in GSW, precipitation, surface temperatures and heat fluxes induced by the effects of terrain irradiance are obvious in mountainous regions, besides, some minor changes are also found in other remote areas due to the circulation alternations. It is also found that in the weather condition with less cloudiness and less precipitation, the effects of slope irradiance can be more realistically shown. Therefore, slope irradiance can normally be neglected in numerical models when the horizontal model resolution is low and the slopes are moderate, and should be included when the resolution becomes high and the terrain steep and rugged