The forecast of rainstorm fall area was done by the rainstorm station number prediction combined with the rainfall forecast of one station.The TS grade of a operational forecast for rainstorm fall area from July to August of 1998 was up to 224%,and more than both HLAFS and subjective forecast.Further,the analysis results show that the method is an effective forecast for rainstorm fall area,and makes the best use of the spatial distribution of rainfall forecast.