In future mobile communication systems, the application of multihop relay system is essential to the coverage extension and capacity enhancement while maintaining the infrastructure cost reduction. And, multicast has been spotlighted as the solution to save resources for high rate multimedia data. But, the proper procedure of multicast in relaying systems has not been researched. In this paper, we propose an efficient multicast procedure considering BS and RS transmission. In the proposed scheme, we do not have to transmit two times multicast services, but BS and RS, which are synchronized, simultaneously transmit the same multicast data through the same resource. The proposed algorithm not only saves resource, but also obtains diversity gain. To evaluate the performances of the proposed scheme, system modeling and simulation are carried out. From the results, it is shown that the proposed scheme could reduce required resources.