Abstract: Based on GRAPES-meso model and T213 data, a series of numerical experiments are carried out to trail a rainstorm process in Sichuan and East China during 18-20 July 2007 in order to analyze the impacts of lateral boundary condition, vertical resolution of T213 data, the model domain of integration, physical process and boundary parameter on the rainfall forecast by GRAPES-meso model.Through four groups of comparative experiments, the main conclusions are as follows:(1) There are only slight impacts of lateral boundary information on this torrential rain forecast.With the qualities of the background fields used in GRAPES-meso model higher, the forecasting accuracy of this rainstorm process are better. (2) Vertical resolutions of T213 data in GRAPES-meso model are very important to the accuracy of this weather process.The higher the vertical resolution is, the better the quality of rainfall forecasting is.And, contrariwise, the weaker the quality is. (3) When the integration domain in GRAPES-meso model is different, the results of precipitation simulations are obvious different.The bigger the model domain of integration is, not always the better the results of simulative rainfall are. (4) The test results using different physical process and boundary parameter show that, the forecast of 24-hour accumulated precipitation is close to the observed precipitation when using WSM 6 scheme and KF eta scheme.