Within a cell of cellular system,cooperative relay technique can improve the performance of multicast efficiently,but it can cause the stream frequent interruptions because of the mobility of relay terminals.A video layered cooperative relay strategy is proposed to guarantee the continuity of multicast stream and retain high-bandwidth of the cooperative relay channel.Based on the capacity analysis for layered relay channel in the strategy,the optimal power allocation is studied to maximize capacity.After analyzing and optimizing the capacity in abstract models,the study is extended to a non-fading and a Gaussian wireless channel model to satisfy the scenario of cellular system.Giving the relay nodes position or distribution of noise power,the obtained results can determine the optimal power allocation among the transmitter and relay nodes.At last,the simulation results show that the strategy and its optimal power allocation have a significant improvement on the performance. Within a cell of cellular system, cooperative relay technique can improve the performance of multicast efficiently, but it can cause the stream frequent interruptions because of the mobility of relay terminals. A video layered cooperative relay strategy is proposed to guarantee the continuity of multicast stream and retain high-bandwidth of the cooperative relay channel. Based on the capacity analysis for layered relay channel in the strategy, the optimal power allocation is studied to maximize capacity .After analyzing and optimizing the capacity in abstract models, the study is extended to a non -fading and a Gaussian wireless channel model to satisfy the scenario of cellular system. Giving the relay nodes position or distribution of noise power, the obtained results can determine the optimal power allocation among the transmitter and relay nodes. At last, the simulation results show that the strategy and its optimal power allocation have a significant improvement on the performance.