Aiming at the problem of resource allocation and interference of D2D （Device to device） communication technology in cellular system， a D2D resource allocation strategy based on the improved genetic algorithm is proposed. Firstly， the power range to ensure the communication quality between cellular users and D2D users is determined， and then an improved genetic algorithm is proposed to determine the optimal transmit power of D2D to maximize the system throughput. The algorithm guarantees the quality-of-service-e （QoS） of cellular system， and makes crossover operator and mutation operator change adaptively with evolution algebra， so as to achieve the global optimization. Simulation results show that the proposed algorithm can effectively improve system throughput and channel utilization of D2D users.