To solve the problems of traditional Ant Colony Optimization (ACO) such as too many nodes in three-dimensional space and difficult algorithm search,a UAV three-dimensional flight path planning algorithm based on Improved Adaptive Ant Colony Optimization (IAACO) is proposed.Firstly,the three-dimensional space is divided into grids,so that the algorithm can be applied to three-dimensional flight path planning.Then,a non-uniform initial pheromone matrix is established,and an adaptive pheromone volatile factor is added,which can improve the searching efficiency and speed up the convergence rate of the algorithm.Finally,the objective function of UAV flight path optimization is further established by defining the 3D length index function and the 3D angle index function,and the global optimization of 3D flight path planning is realized.The simulation results show that the proposed algorithm has shorter running time and faster convergence speed,and the planned flight path is also shorter and smoother.