Construction bidding is dealing in future contract of fixed price first and made bargain： 拍板成交；成交 later, which decide that bidding is a high-risk activity. Quoted risk is object, uncertain and losses, bidder must correctly assess quoted risk if he hopes to manage project successfully. The article have built unit price risk assessment model based on AHP, gathered and neaten subjective judgment, ascertained hierarchic layers according to correlation and subordinate relationship, formed a layer system of risk factor, gotten judgment matrix and weight vector, quantified risk loss of every subproject, obtained the quoted risk ratio. All ensured bidder can find the critical risk control point and date back to subproject where the risk existed. So bidders can manage risk actively and prospectively. Exemplified risk assessment model of a residential house bidding in Hangzhou at last.