Traditional power allocation schemes have ignored channel estimation errors and circuit energy consumption. To solve this problem, an improved green joint optimization scheme was proposed in this paper. On the premise of guaranteeing user's QoS (Quality of Service), energy efficiency and time efficiency for relay selection and each relay's power allocation were jointly optimized in the improved scheme, with taking channel estimation errors and relay circuit energy consumption into consideration. In the end, the closed solutions of transmit power of the source node and relay nodes were obtained. The simulation results show that the proposed scheme performs 30% better than traditional optimization scheme in energy efficiency with high SNR (Signal-to-Noise Ratio) and has a close performance with low SNR.