In this study, the resource blocks (RB) are allocated to user equipment (UE) according to the evolutional algorithms for long term evolution (LTE) systems. Particle Swarm Optimization (PSO) algorithm is one of the evolutionary algorithms, based on the imitation of a flock of birds foraging behavior through learning and grouping the best experience. Therefore, we propose a Simple Particle Swarm Optimization (SPSO) algorithm for RB allocation to enhance the throughput of Device-to-Device (D2D) communications and improve the system capacity performance. The simulation results show that with less population size of M=10, the SPSO can perform quickly convergence to sub-optimal solution in the 100'h generation. Therefore, as compared to the random allocation (Rand) method, the proposed SPSO can obtain sub-optimum performance with more 2 UEs than the Rand method.