By combining the improved interfered fluid dynamical system and grey wolf optimizer, a hybrid method is adopted for three-dimensional path planning of the unmanned aerial vehicle(UAV) in complex terrain environment. The improved interfered fluid dynamical system is mathematically modeled. By modifying the original flow, the disturbed fluid is obtained, where the streamlines can be regarded as planned paths. The problems of the stagnation point and the partial trap can be solved effectively. Then, by imitating the hierarchy and predation strategy of wolf pack, as well as the individual memory and the rules of survival of the fittest, the reactive parameters of obstacles are optimized. Simulation results show that the planned three-dimensional route is smooth, feasible and of good obstacle avoidance behavior.