Abstract: This paper discusses the methods of using of information entropy to determine the weight of indicators and the basic principles of Gray decision-making, on basis of which it sets up a mathematical model correspondingly. It applies the nonequivalent weight Gray situation decision-making methods into the decision-making of the construction projects bidding, and covering a number of uncertainties and risks in the presence of tender. It determines the goals of the Gray situation decision-making from the factors of the construction tender, and makes the decision tree and standard variation (risk value) as a quantitative objective of the decisionmaking so that the basic data source of the method of Gray situation decision-making is much theoretical. In the last part, the paper expatiates the bidding decision-making process combining the examples of projects, and the results of the decision-making. Finally it provides the base for the construction contractors to make the right decisions in bidding.