Abstract: Aiming at the problem of the optimal joint power allocation for cooperative multicast communication systems in the wireless networks with non-regenerative relaying,a new transmission scheme based on the multi-user diversity-cooperative protocol(MDP) is adopted.When the total power is constant,diversity-multiplexing gain tradeoff is used to analyze system performance.Taking the minimum SFEP(system frame error probability) as target,an optimal power allocation scheme between source and relay is designed.With the lower bound of SFEP in high SNR(signal noise ratio) as the objective function,the optimal solution of system power allocation is obtained by Lagrange multiplier method.Simulation results show that compared with the network using traditional transmission scheme,the network adopting transmission scheme based on MDP possesses higher ceiling in diversity gain and multiplexing gain,therefore,has better system performance.