The aim of this study was to establish the prewarning and prediction system for crop diseases and pests based on SuperMap IS. NET geographic information system (GIS), which was developed by Supermap company. In this system, the authors used visualization and spatial analysis with GIS, and the large area remote sensing (RS) to acquire the information of crop diseases and insect pests. Based on these data, the occurrence and damage of various diseases and insect pests of crops could be monitored and forecasted in real time and in large areas. And ultimately, the system could transform data information into a geographical information map to show the occurrence degree and distribution on variety of diseases and pests. This paper described mainly warning flow, database design and the main functions of the system. Finally, the system realized successfully the warning of the wheat stripe rust in Xifeng region of Qingyang city in Gansu province in 2002, and the prediction result was satisfactory. It indicates that the system can classify and predict diseases and insect pests, and people can select right time and technology to control the diseases and pests by this GIS system.