The Weather Research and Forecasting model(WRF) was used to simulate the formation process of Meiyu in 2004 and the impact of urbanization on precipitation and the vertical structure of the Meiyu front was analyzed in detail.After changing urban to cropland,the simulated precipitation at rainfall centers on June 14 decreased obviously,while the precipitation over the area northwest to it increased.The thermal structure of Meiyu front was similar to that in the control experiment,but the intensity of the high value scope of the pseudo equivalent potential temperature,ascending motion,convective instability and moisture were weaker.The location of the frontal zone was slightly north than in the control test.On June 15,the simulated precipitation at the rainfall center in the middle of Anhui Province also decreased,and the precipitation over the area west to it increased.The structure of the Meiyu front and the location of frontal zone were similar to those in the control run,but the low value scope of the pseudo equivalent potential temperature(336 K) at 800 hPa was larger,almost covering 26—32°N,resulting in lower convective instability over the high value region of the pseudo equivalent potential temperature.