This paper studies the location and tracking problem of the over-the-horizon target(OTHT).A new method is proposed

which uses active tracking technology and time difference of arrival (TDOA) location method to track the OTHT.This location system is composed of several air platforms and ground stations.The target signal is transmitted (or reflected) by air platforms and received by ground stations.TDOA information is measured by ground stations.At the same time the position of air platform is located by active radar in ground station.Then the time of target signal propagated between air platform and ground station is obtained.By simple calculation we can obtain the TDOA information of these air platforms

which is used to locate the OTHT.Simulation results show that the OTHT can be located and tracked by the method proposed.