Each party in engineering project faces different quality risk in different stage,and each adopts different management decision against quality risk.Firstly,from the new classic economics angle,an economic explanation to the management decision against engineering quality risk according to the different benefits for contractor and owner.The owner and contractor of a construction project,the government and projection legal person find their economic ties in an asymmetric information supply,or in an imperfectly assigned contract.The rules and characteristics of entrust-agency relation are analyzed from the economics and information economics angle,an economic explanation of engineering quality risk is given according to entrust-agency relation.The measures of controlling quality risk have been put forward from the angle of the economics.