Abstract: Automatic dependent surveillance-broadcast (ADS-B) are facing an increasingly serious malicious spoofing problem. Multi station passive time difference of arrival (TDOA) location ADS-B anti-spoofing method is an effective method for identifying and locating spoofing source. However, in the existing TDOA location methods, there also exist some shortcomings, e.g., high time synchronization cost between stations, vulnerable to global navigation satellite system (GNSS) regional interference, etc. Aiming at the above problems, this paper proposes a new distributed passive location ADS-B anti-spoofing method based on opportunity reference source. By dynamically selecting some trusted ADS-B targets as opportunity reference sources, this proposed method can realize multi station synchronization, and effectively overcome the bottleneck problem of some existing TDOA location methods. It is shown from the simulation results that by optimizing the ADS-B opportunistic reference source in the presence of a large number of ADS-B real sources and spoofing sources, the proposed method can not only accurately identify false ADS-B message, but also achieve accurate inter-station synchronization. Moreover, via the accurate inter-station synchronization, the spoofing source can be accurately located.