Abstract: This paper introduces and analyzes systematically the principle, process and parameters of particle swarm optimization (PSO) algorithm, and their influence on optimization performance of PSO. Various improved particle swarm optimization algorithms are discussed. The algorithm principle and algorithm parameters of multi-phase particle swarm optimization (MPPSO) algorithm, and their influence on optimization performance of MPPSO are analyzed. At last, applications of PSO algorithm are discussed, and further research issues and some suggestions are given.