In terms of the defects, such as poor interaction and slow response, of traditional WebGIS, through in-depth study of the Flex technology, we propose an application framework developing WebGIS with Flex. We describe each part of the implementation in detail, and analyze the problem in this framework, that is serialization of task calls can not be implemented in the Flex presentation layer, then give specific design and implementation scheme. Through the application in the Emergency Rescue Command System, it turns out that this framework not only enhances the interaction of WebGIS, improves the efficiency of development, but also can efficiently implement the serialization of task calls, obtains satisfied results.