Resource-constrained project scheduling problem (RCPSP) is a well known NP hard problem. This paper proposes a hybrid approach of constraint programming (CP) and integer programming (IP) which could solve RCPSP with ideal efficiency and quality. Constraint propagation is key element of constraint programming and is widely used in cumulative resource problem (CRP). CRP can be taken as a relaxed problem of RCPSP. This paper discussed how to eliminate the resource constraint, and transform RCPSP to project scheduling problem (PSP) so that the problem will became easier. Experiment shows this hybrid approach has certain efficient advantage compared with traditional CP method.