Abstract: The programming design of Agrometeorological Yield Forecasting Operational System (AYFOS) is programmed with the languages of Quick BASIC, MS-C and MASM. The prompt message is given by using pull-down pop-up Chinese menu. The help function is provided by man-computer interaction with color highlight bar. The system has reasonable software structure, convenient operation and high quality product output of tables and graphics. It consists of six functional modules including data management, forecasting model building, forecasting model memory, real-time forecasting and forecasting model integrating, product output management and system maintenance. This system posseses a general operational software and it is objective and convenient for agrometeorological yield forecasting.