Abstract: This paper proposes an approach of 3D route planning based on A* algorithm.This approach could directly search optimal route in 3D environment with route constrains,which discretizes the long range missile kinematics model and uses the overload of missile as control flow.The process of route planning not only integrates the maneuverability of missile,but also adequately uses the terrain information in terrain-avoiding and threat-avoiding.Simulation results demonstrated the method could obtain optimal route in 3D environment,which could adapt to overload constrains.