In order to solve the problem that the ADS-B ground station monitoring for the flight situation of the general-aviation aircraft makes it difficult for the aircraft itself to perceive the flight situation of the surrounding aircraft, a situation monitoring terminal system based on ADS-B IN is designed for general-aviation aircrafts. The system adopts a microcontroller to parse the received messages of ADS-B, and uses Android Studio to design terminal display software. At the same time, the improved Residual Mean Interaction Multi-Model（RMIMM） algorithm is used to perform track filter processing for the position and state information of the aircraft, thus to improve the flight state estimation accuracy. The improved algorithms and systems are validated by using the data received through actual devices. The results show that, the terminal system can effectively sense the flight situation of the aircrafts around the general-aviation aircraft and improve its flight safety.