After all kinds of problems such as budget dis - control, low construction quality of public project construction, and bureaucrat corruption in China are introduced, the causes of all the problems lies in the shortage of effective budget constrain, risk identifying and risk controlling mechanism are analyzed in the paper. The validity of buyers monopolistic market of invited public bidding of public project construction and its budget controlling function are analyzed in the paper. And the principles and suggests of effective identifying and controlling all kinds of risks of public project construction, such as bureaucrat corruption and low construction quality are put forward. The important theoretic and practical meanings of the research are to improve construction quality, promote normative development, and greet international competition of public project construction in China.