Based on the NWP products,the medium--range operational .forecasting system of a microtherm and excessive rain in spring is established. The system includes detailed data of the microtherm and excessive rain as well as continuous fine days. It uses successive regression,successive discrimination and analog method to combine NWP products with synoptic principles andforecasting experiences. The system can collect data and make prediction automatically and objectively. Every part of the system is independent. The system uses batch processing technique andcan be operated easily,and it displays data and figures rapidly.The results of the experiments in the last three years show that the system has better abilities in forecasting rnicrotherm and excessive rain. Obviously social and economic benefits havebeen obtained in the practical forecasting operation.