A regional air–sea coupled model (RegCM3-POM) is used, and the ability of the model to simulate June, July, and August (JJA) moisture transport is verified. The coupled model (RegCM3-POM) has better performances than the uncoupled model (RegCM3) in the simulation of the JJA mean water vapor characteristics from 1979 to 2002 and its interannual variations. The differences of water vapor between RegCM3-POM and RegCM3 are mainly caused by different winds in the middle and low troposphere. The simulated circulation pattern of RegCM3-POM is more similar to the Climate Forecast System Reanalysis (CFSR) data than that of the uncoupled model. The simulated geopotential height and the gradient of geopotential height in the coupled model are more accurate than those in the uncoupled model. The real-time and lead–lag relationship between geopotential height and sea surface temperature (SST) in RegCM3-POM is consistent with that between the height of CFSR data and HadISST (Hadley Center Sea Ice and Sea Surface Temperature data). Thus, the simulated water vapor in the lower troposphere and the vertically integrated moisture transport are more accurate in the coupled model than in RegCM3. In addition, the correlation coefficients between moisture transport and SST in RegCM3 are positive in South China Sea, corresponding to SST forcing; the correlation coefficients in RegCM3-POM are negative, which is consistent with that between the vapor transport in CFSR data and HadISST. Thus, the air–sea coupled model represents more accurately than the uncoupled model the relationship between SST and moisture transport.