Two-unmanned-aerial-vehicle (UAV) cooperative target locating based on airborne visual tracking platform is a common UAV reconnaissance mode. In the process of two-UAV cooperative target locating, the performance of target locating is highly dependent on UAV trajectory. In this Letter, a trajectory planning method for two-UAV cooperative target locating is presented. Using the line-of-sight (LOS) targeting property of the airborne visual tracking platform, in combination with the azimuth angle and elevation angle of the measured LOS, a locating error model is established, which can reflect the correlation between the target locating error and LOS angle error. Then an objective function based on minimising the target locating error is built, which is used as an index of two-UAV trajectory planning. This method can be applied in two-UAV trajectory planning for cooperative target locating and the simulated results confirm that it works effectively.