The invention relates to an anti-UAV (unmanned aerial vehicle) passive detection and direction finding positioning system which comprises an array antenna, a radio frequency switching switch, a double-channel receiver, a dual-channel signal processor, a wireless router, a positioning server, and a monitoring terminal. Through the antenna array, the measurement and control and image transmission radio frequency signals emitted by a UAV and an operator are passively intercepted and received, the double-channel receiver carries out frequency conversion of the intercepted and received signals into intermediate frequency signals, the signal detection and parameter estimation of the intermediate frequency signals are carried out, and the characteristic parameter of the UAV is obtained and is sent to the positioning server through the wireless router. After the positioning server receives the characteristic parameter of the UAV, the characteristic parameter of the UAV is subjected to direction finding cross positioning, and the detection, positioning and tracking of the UAV are realized. According to the system, the positioning and tracking of the UAV are realized so as to satisfy safety guarantee of an important key area and UAV countermeasure and interference requirements.