Abstract: This paper utilizes the latest version of Regional Climate Model (RegCM4) with three different horizontal and vertical resolutions to simulate the regional climate in China during June to August, 2001-2003. The simulated precipitation is compared to the GPCP (Global Precipitation Climatology Project) precipitation at daily, monthly and seasonal time scales in an effort to study the influence of spatial resolution on summer precipitation simulation. The main conclusions to come out of this study are the following. The new version of RegCM4 is able to better simulate the distribution pattern of precipitation. Simulated precipitation amounts tend to decrease from southeast to northwest, and the amount decreases with the increase of both horizontal and vertical resolutions. Precipitation simulated with horizontal grid spacing of 30 km and 14 vertical levels will have the least bias among the all experiments. The sensitivity of simulated precipitation to the model resolution varies differently over different regions and at different times of the year. The spatial resolution will have more influence on precipitation simulation in higher altitudes. The simulated peak value of daily precipitation decreases with the increase of spatial resolutions. The resolution will have more profound impacts on the low-frequency bias and the 24-day period component in the daily precipitation series. Thus, the system error can be reduced effectively by adjusting the model spatial resolutions.