Abstract: In this paper based on mean generating function principle,the experimental forecast with stepwise sieving model and Empirical Orthogonal Function (EOF) model of mean generating function have been made. We put forward a new kind of EOF model with stepwise sieving,and all of the three forecasting models have been experimented on precipitation sequence with great variation amplitude. The result shows the EOF model with stepwise sie ving is better than EOF model alone,and another result which forecasts have been experimented by different forecast step-length also shows EOF model with stepwise sieving is very good in the respect of forecast effect and model operation stability.