Abstract: A brief discussion is made on the conception, advantages, data flow of the three-layer structure, and the communication mode, based on the COM technology, between the application server and client programs. The application of the three-layer structure method to the meteorology information processing systems is described through the examples of rainfall editing and rainfall summing in a period of time to explain in detail the developing process of the three-layer structure system. Based on it, the general method, the related principles and skills for developing the application server and client programs using DELPHI 4 are presented.