Multi-divided particle swarm optimization is putted forward based on dichotomy particle swarm optimization. Aims at how to confirm the number of divided particle, how to evaluate the ability of particle optimization and the ability of algorithm optimization, linear array synthesized pattern’s performance are studied by defined the rate of particle stagnancy and the rate of optimization, which involves low side-lobe beam pattern synthesis and low side-lobe beam pattern with nulling synthesis. The results of simulation indicate that the more times of particle divided the higher of optimization rate, and the constringency speed of PSO is fast, but the rate of particle stagnancy is almost same. However, more times of particle is not always good when synthesizing complex beam pattern. These characters show that the two indexes which can availably reflect the ability of particle optimization and algorithm optimization, can reliably estimate optimization ability of multi-divided particle swarm optimization from microcosmic point.