The initial model of Shanghai regional numerical ensemble forecast system is established based on Shanghai regional operational numerical forecast model. In this system, eight forecast members are created according to the model uncertainty. Daily 48 h experiments are made for summer 2004. The results show the ensemble mean forecasts of precipitation,temperature and sea level pressure for cities in East China are not worse than the forecasts of the operational model, although the horizontal resolution of the operational model is three times as the resolution of the ensemble model. The ensemble mean forecasts of large precipitation,minimal temperature and 0～24h sea level pressure are better than the forecasts of the operational model. Also objective and quantitative precipitation probability forecast can be obtained from the ensemble forecast. The precipitation probability forecasts have good directions for the happening of large precipitation in the near future.