In water environmental monitoring

unmanned aerial vehicle（UAV） can not monitor all the areas at a time due to the influence of its physical properties and risk factor.So it’s extremely important to bring the service efficiency of the UAV into full play.The optimal path planning problem of the UAV for water environmental monitoring is presented and a mathematic model of the problem is built up.On the basis of this

a geneticsimulation annealing algorithm is presented.The computational amount is decreased

a method combined of both grid space indication and directional code is adopted.The simulation test result indicates that this method can get a better solution than genetic algorithm and it can resolve the path planning problem of the UAV for water environmental monitoring effectively.