Abstract: Since the periodic extension of mean generating function in regression analysis has the defect of unequal premise,and the predictors are not independent to the predictants.An improving scheme is suggested.Analysis and experiment so fsam plesresult in that the new scheme can effectively eliminate the false correlation appearance which exist in old scheme,so the selected periodic predictors are more objective.Basing this new mathematical model,fitting rate and forecast accuracy is basically identical.It is a very useful method for long-term prediction and analysis.What is more,this model has some resolving power of hidden eriodicity.