In the past two decades，health policy in China has undergone considerable transition which led to a multiple and even conflicting institutional environment of hospitals.In this article the theory of institutional logic from new-institutionalism is applied to explain the dual institutional constraint on social work practice in a non-profit hospital in Beijing.Because of the path choice of medical reform，institutional logics of hospitals mainly consist of two contradictory ones，including market-management logic and social service logic.Although they direct and constrain hospital’s behavior，organizations have their own action choice and strategies to cope with the conflicting institutional requirement.The article stresses the agency and strategies of social workers in social rehabilitation department in a hospital.Borrowing new rules，coping with uncertainty and relying on an identity are three main strategies which the social rehabilitation department used to follow the institutional constraint and requirement of legitimacy.However，social work practice in the conflicting institutional environment at last resulted in the deficit of professionalization and goal displacement.The author concludes that the process of professionalization is not a natural knowledge accumulation but embedded in specific institutional settings and organizational situations.