Abstract: In the practical multitarget tracking system, the good tracking accuracy and the good concealment always are demanded at the same time, but the infrared-radar data fusion system could hardly meet this demand before. Therefore, in this paper, the problem of multitarget tracking in cluttered environment by infrared-radar track fusion with infrared as the main sensor(always work) and radar as the subsidiary sensor (intermission work)has been thoroughly studied. Under the condition of the special sensor work mode,large amount of simulation work is done to prove the effectiveness and unique advantages of the above system.