Abstract: Land surface processes affect the climate through exchanges of materials (e.g., water) and energy across the land－atmosphere interface, and their parameterizations play an important role in numerical weather forecasting and global and regional climate studies. In this work, the Common Land Model (CoLM), with biophysical and biochemical process parameterizations, is coupled to the regional climate model RegCM3 by replacing its original land surface scheme BATS. The newly coupled model is called C-RegCM3 hereafter. Simulations by C-RegCM3 for summer climate of a flooded year over East Asia are undertaken to validate the newly developed model. C-RegCM3 shows reasonable results of general atmospheric circulation, near-surface air temperature and precipitation, and it improves the simulation of precipitation in the semi-arid region of Northwest China. Comparisons of simulated surface energy and hydrological processes by C-RegCM3 and those by RegCM3 indicate that C-RegCM3 tends to get more latent heat fluxes but less sensible heat fluxes in the semi-arid and semi-humid areas, while the region, where obvious difference between the absorbed solar radiation from C-RegCM3 and that from RegCM3 exists, is located in the simulated rainy areas. The simulated soil moisture at the surface by C-RegCM3 tends to be drier, which is consistent to less precipitation and more evapotranspiration in this region than that by RegCM3 in the transition zone of semi-arid and semi-humid areas during summer. It means that the simulated positive feedback of soil moisture－precipitation－evapotranspiration by C-RegCM3 is stronger than that by RegCM3 over the transition zone.