Abstract: An algorithm is proposed for energy-efficient user scheduling and resource allocation scheme in multi- user OFDMA mobile communication downlink system. A mathematical formulation of optimization issue is provided with the objective of maximizing system energy-efficient under QoS constraint. The proposed method can use system diversity to implement user selection and rate allocation with perfect Channel State Information (CSI) at the base station, it also enhanced the usage of energy effectively. Simulation results demonstrate that the performance of proposed algorithm is close to the optimum, it also has low complexity.