先用BP神经网络算法对国民经济生产总值做预测，然后用灰色预测模型GM(1,1)做预测，最后将两者结合建立组合预测模型。-Firstly,the BP artificial neural network algorithm to predict the GDP and then construct the GM(1,1) model,at last build out the combined model to predict the GDP int the future.