China is a country with complex topography, land surface conditions, coastlines with the world highest plateau in its west and the largest ocean at its east, and with large contribution from mesoscale phenomena, such as the mei-yu frontal systems and tropical storms. To study the regional climate in such a region, a highly resolved regional climate model (RegCM) has been recently developed at the International Pacific Research Center (IPRC). The distinct features of this model include direct feedback of cumulus detrained cloud ice and cloud water into the grid-resolved quantities; the effect of cloud buoyancy on turbulence production with mixed-ice phase clouds; an explicit coupling between the cloud microphysics and radiation via cloud properties; an explicit coupling between land surface and radiation via surface albedo, direct and diffuse radiation fluxes; and the effect of frictionally generated dissipative heating. The performance of RegCM3 is demonstrated by its simulation of the 2003 summer extreme climate event over the whole China region including Tibetan Plateau. There have not had so many studies about this region on this regard. With the use of the NCEP Reanalysis 2 data provided by the NOAA-CIRES Climate Diagnostic Center, Boulder, Colorado, USA, from their Web site at http://www.cdc.noaa.gov/, which is available at 6hr intervals with a resolution of 2.5°×2.5°, as both the initial and lateral boundary conditions, the model was integrated from 1 May to 31 August 2003 with a resolution of 60km×60km covering the area of 15°-55°N, 70°-140°E. It is demonstrated that the RegCM3 has a pronounced rainfall downscaling scale, producing more realistic regional details and overall smaller biases than the driving reanalysis data. The model simulated realistically not only the temporal evolution of the area-averaged precipitation and the monthly mean precipitation spatial pattern but also the daily precipitation intensity distribution.