Bidding evaluation decision support system overcomes the shortcomings like subjectivity and uncertainty in traditional bidding evaluation. It takes full advantage of history data to provide decision making support in bidding evaluation. This paper presents a data mining model based on neutral net algorithm, analyzes and studies its features and establishment, then applies the model in the hydropower project bidding evaluation decision support system, with the practical business demands of hydropower project bidding, to implement a fair and rational hydropower project bidding evaluation decision support system.