Both tenderees and tenderers attach much importance to contractor prequalification before bidding because it plays important roles for both and so far the Score Method has been widely used in our country. But the weights in the method are man-made, which may be affected by personality inevitably. In order to avoid this influence, this thesis will introduce another method based on artificial neural network. This thesis expatiates the principle of artificial neural network, and analyzes the characters of prequalification. Then, the author sets up the mathematics model. In the end, the author analyzes this method by an example.