The invention discloses a path planning optimization method for a quadrotor unmanned aerial vehicle based on an ant colony algorithm. A three-dimensional grid map technology is used to divide a planning space, a three-dimensional environment map based on a three-dimensional grid map is drawn, and finally the path planning of the quadrotor unmanned aerial vehicle is carried out. A high-level three-dimensional environment model is established during model establishing by considering the self characteristics of the unmanned aerial vehicle and the complex environment of the outside in order to reduce the probability of encountering an obstacle. In the aspect of planning algorithm, path searching is completed through adopting the three-dimensional ant colony algorithm by selecting a main direction, and a variable main direction search strategy and a path simplifying strategy are adopted in algorithm improvement to successfully solve the problems of the path directly passing through the obstacle, many searched path nodes and too large fitness value, caused by direct connection between two planes during path searching adopting traditional basic three-dimensional ant colony algorithms in order to avoid the obstacles, so the path length is reduced, and the searching efficiency is improved.