In order to improve the operation efficiency of the unmanned aerial vehicle (UAV) on mountain region, the fourrotor UAV was used as the test object. The energy efficiency coefficients of the threedimensional motion were proposed through the force analysis and simplification of the threedimensional motion of the UAV. Then the performance of the UAV was tested and the correlation model between power and thrust was fitted with the coefficient of determination of 0.9894. The energy efficiency coefficients under different load conditions were calculated on this basis. After that, the optimal energy consumption operation paths of UAV on mountain region were simulated based on the correspondingly designed simulated annealing algorithm (SAA). The test results showed that when the flying speed of the UAV was 2m/s, under different constant loads, the optimal energy consumption paths can save up to 30.16% of the energy compared with the conventional paths, and 5.47% of the energy compared with the shortest paths; in the case of the realtime changing load, the optimal energy consumption path can save energy by 32.04% compared with the conventional path and save energy by 11.72% compared with the shortest path. It showed that under the constraint of energy consumption, the simulated annealing algorithm can optimize the operation path of the UAV to save energy, which was of great significance for improving the operation efficiency of the UAV on mountain region.