Abstract: Particle swarm optimization(PSO) with neighborhood operator is adopted to deal with(vehicle) routing problem(VRP) with non-full load.An improved PSO algorithm is proposed,in which a real method is designed,inerita weight is adjusted linearly,and uptate equations are modified.Two VRP(examples) are solved by this algorithm,and the results are compared with those by both genetic algorithm(GA) and standard PSO.The(results) indicate that the modified PSO can improve success rate of searching best route and is more effective for VRP with non-full load.