On the basis of Artificial Neural Network theory, a back propagation neural network with one middle rnlayer is building in this paper, and its algorithms is also given, Using this BP network model, study the case rnof Malian － River basin. The results by calculating show that the solution based on BP algorithms are consisrntent with those based multiple－variables linear regression model. They also indicate that BP model in this rnpaper is reasonable and BP algorithms are feasible.