On basis of the combined model of wavelet analysis and support vector machine (WA - SVM), this paper decomposes the original rainfall series to different layers by means of wavelet analysis, then forecasts each layer by means of SVM, and finally obtains the forecasted results of the original time series with composition. This model to estimate the monthly rainfall sequence in the watershed has been applied for the basin rainfall forecast, and the data obtained by combined model are compared with the results obtained only using support vector machine(SVM). 