This paper studies PMD compensation problems in the optical communication. In an adaptive compensation process of a practical PMD compensator, three main parts are included: an equalizer, a detection part and an algorithm. In order to achieve faster and simpler, particle swarm optimization (PSO) algorithm was introduced to this process. Although the original PSO algorithm is easy to trap into sub-optima, we proposed a new modified PSO to avoid sub-optima but keep the simplicity at the same time. This is the first time to introduce the conception of collision into PSO arithmetic, so it is called collision PSO. Through the numerical simulation, this proposed method showed the better result than the original PSO methods.