Aiming at the problem that unmanned aerial vehicles (UAVs) have no signal or insufficient positioning accuracy in GNSS-denied environments such as basements and tunnels,and cannot realize autonomous route planning of UAVs,a UWB high-precision UAV positioning system that can be applied to existing UAVs is proposed.The symmetric bilateral bidirectional ranging algorithm is adopted in this system,which simplifies the computational complexity and introduces the ratio of the first path power to the cumulative channel impulse response power to suppress the NLOS error.A GNSS message simulation model is designed to convert the local coordinates into standardized GNSS messages to simulate GNSS receivers.The experiment results show that the system realizes the high-precision positioning of UAV in GNSS denial environment,and the root mean square error of positioning is less than 0.5 m,and the reliability is 99 %.