A bare bones particle swarm optimization(NPSO) algorithm is proposed to improve both global exploration and local exploitation. An evolution equation which obtains better swarm diversity is employed in the NPSO algorithm. Inspired by the apical dominance phenomenon in biology, a particle pruning strategy is introduced as follows: When a particle reaches a new best position of the swarm, it would be pruned and inserted to another position. Theoretical analysis shows that the pruning strategy can improve both global exploration and local exploitation. Finally, results of the experiments on benchmark problems show that the proposed algorithm obtains significant improvement when compared to some classical PSO algorithms.