Debris flow prediction is one of the important means to reduce the loss caused by debris flow. This paper built a regional prediction model of impending debris flow based on regional environmental background (including topography, geology, land use, and etc.), rainfall and debris flow data. A system of regional prediction of impending debris flow was set up on ArcGIS 9.0 platform according to the model. The system used forecast precipitation data of Doppler weather radar and observational precipitation data as its input data. It could provide a prediction about the possibility of debris flow one to three hours before it happened, and was put into use in Liangshan Meteorological Observatory in Sichuan province in the monsoon of 2006.