Abstract:The fourth-party logistics company alliance building problem is to study how to build alliance with a method of high efficiency and low cost. An improved algorithm about graph clustering based on Particle Swarm Optimization (PSO) was proposed to solve the problem, and it contributed to reduce the connection cost between companies in the group. Discretization PSO was used to optimize the clustering result of graph clustering algorithm, and the result with disturbance strategies got enhanced. Clustering the 100 virtual companies, the cost was reduced from 39991 to 24800. The experimental result shows that, the improved graph clustering algorithm based on discretization PSO can solve the problem in a way with high efficiency and low cost.