Air Traffic Collision Avoidance System (TCAS), as a compulsory equipment by ICAO, can provide two levels of alert, traffic advisory (TA) and vertical resolution advisory (VRA), but there is no horizontal traffic collision avoidance alert provided by TCAS so far. This paper focused on the algorithm of horizontal traffic avoidance. Through the fusion of tracks of ADS-B and TCASII. We can improve the aircraft track accuracy judgment so that realize the horizontal avoidance and alert. There is a new track detection model and algorithm raised by this paper to solve the problem of horizontal turn collision avoidance, and with MATLAB, optimized collision avoidance turn direction and angle can be achieved.