Abstract: The investment, schedule and quality of a project are taken as variables to construct the multiattribute utility functions of the two sides of a contract. The relationship between the utility values of the two sides and at the counterpoise point and the factors affecting the relationship are studied through the analysis of the Nash solution to their game playing. The causes of claims are analyzed according to the changes of the utility counterpoise points. The study is helpful to explain the phenomenon‘biddingwith low price, profiting by claim’