Abstract: Based on the ray tracing algorithm of Taylor series approximation, the propagation path simulation model of over-the-horizon target time difference of arrival (TDOA) location system within 1 000 km is carried out. The differential time delay error and multipath relative delay under different atmospheric duct environments are calculated and analyzed, and the delay difference accuracy of TDOA positioning system aimed to over the horizon target is evaluated. The results show that the differential time delay error of passive location system increases with the increase of communication distance due to the variation of atmospheric refraction environment with distance. When the communication distance of the system is close to 1 000 km, the differential time delay error can reach nearly 30 ns and the relative multi-path delay can reach nearly 20 ns under the strong surface duct environment, while the time delay difference at 1 000 km communication distance can reach nearly 40 ns and the relative multi-path delay can also reach nearly 20 ns under evaporation duct. Through the quantitative analysis of the time delay of the over-the-horizon link caused by atmospheric duct, the environmental protection and technical support is provided for the performance and parameter design of the passive TDOA location system.