The selection of naval ship principal dimensions based on Particle Swarm Optimization (PSO) algorithm was presented. Firstly, at the foundation of single-scheme decision making method using weighted distance to ensure the consistency, a new multiple-scheme group decision making method was proposed. Secondly, experts’ opinions were judged and adjusted by PSO, in order to keep the initial preference of the individual. Thirdly, the new method is introduced to group decision making of naval ship principal dimensions. Through determining the attributes and their weights, a series of schemes are generated by uniform design, then numbers of experts were invited to make a rational evaluation for deriving the final result, its consistency is better than the one derived without restriction of weighted distance. This new decision making method offers an effective and efficient way to determine the naval ship principal dimensions with high reality and reliability.