In order to solve the optimization problem of undervoltage load shedding（UVLS） parameters quickly and effectively， a distributed computing method based on an enhanced particle swarm optimization（PSO） algorithm is presented. The problem is described as an optimization model with a L ∞norm objective function. Two rules for the comparison of particles are introduced to keep infeasible solutions near the boundary so as to improve the search efficiency. The strategy of performing global search and local search alternately is adopted to speed up convergence. Furthermore， an approximate strategy of contingency simulation is proposed which can reduce the computational burden effectively. The results of a real power grid in China show that the proposed method not only improves the computation speed evidently， but also obtains satisfactory optimization results.