Abstract: The combination forecasting is to weight results of the forecasting used by different methods. In this paper, a new algorithm of forecasts, the Frank-Wolfe algorithm, corresponding to a combinative forecast model based on the principle of OLS is presented. Its application to the forecasting of internal corrosive rate of gas pipeline shows that it has the highest precision in forecasting. Therefore, it is a simple and effective method of combinative forecasts in solving combinative forecast weight.