To address the problem of space locus searching, a slowdown particle swarm optimization (SPSO) is proposed to improve the convergence performance of particle swarm from the position viewpoint. The particle swarm in SPSO is divided into many independent sub-swarms to guarantee that particles convergent to different position, since space locus has multiple optimal solutions and requires the convergence of both fitness and position of particle. Furthermore, particle velocity is updated by half according to fitness to achieve the position convergence. The simulation results show the advantage of the proposed slowdown particle swarm optimization-SPSO, which leads to an efficient position convergence.