Abstract: In order to solve the flight path planning problem of multi-replenishing-point multi-UAVs plant protection operation, a UAV environmental information model and operation area division based on Voronoi diagram were established, and a flight path planning algorithm based on particle swarm optimization（PSO） was proposed. Four factors including effective operation path, total path, total energy consumption and turn times were fully considered. Perform full coverage path planning for known areas. The simulation results show that PSO algorithm improves the effective operation rate by 2.55% compared with the traditional breakpoint continuation flight method. The total path, total energy consumption and comprehensive cost are reduced by 2.55%, 3.45% and 1.04% respectively. Under the PSO algorithm, the effective operation rate of plant protection UAV is higher, the invalid path is shorter, the energy consumption is lower, and the economic cost is reduced.