Abstract: The Xi'an Metro Cable incident exposed the government's serious problems with the procurement of public works materials. In this paper, big data research found that the phenomenon of bidding below the cost price also exists in the bidding and purchasing of power grids. In the non-standard tender bidding projects, the drawbacks of the lowest bid winning bid evaluation method have become increasingly prominent. Based on the lowest bidding model of sealed price bidding, considering the quality of power grid materials and the delivery schedule, the incomplete bidding game theory is used to analyze the low bidding phenomenon existing in the grid procurement market. As the quality of the bidding suppliers' materials can not be completely recognized by the owners, under the profit driven by low-cost suppliers, there is a certain risk of contract default risks such as jerry-building and the phenomenon of adverse selection in the entire power grid procurement market. Through the principal-agent model, the mechanism and the optimal bidding scheme to overcome the defects of the low bidding system can be obtained: as the independent third party involved in the game, the market supervision agency is introduced; the hierarchical evaluation mechanism of material suppliers is established through repeated games to promote the material purchasing market healthy growth.