In order to improve the performance of multi-antenna troposcatter communication system， a multi-antenna adaptive frequency selection diversity method is proposed. By comparing and analyzing the receiving SNR distribution characteristics of different adaptive frequency selection diversity methods under multi-antenna system， the diversity method can obtain the best diversity performance and can be applied to multi-antenna troposcatter communication system. Simulation results show that the performance of the multi-antenna adaptive frequency selection diversity method is better than the existing diversity method and can effectively improve the performance of troposcatter communication system.