Aiming at the problem of variable sampling rate sensor multi-target tracking in clutter,considering the ability that Secondary Surveillance Radar(SSR) can identify enemy or friend target and enhance the accuracy of tracking enemy target,a SSR modified unscented Joint Probabilistic Data Association(JPDA) tracking algorithm is proposed for multi-sensor asynchronous system. Firstly,by using asynchronous data dealing way of mapping measurements,point track of the multi-sensor measurements is composed. Secondly,SSR is used to modify the height information of the enemy target adaptively. Finally,by using the unscented JPDA algorithm,the sequential filtering fusion of asynchronous sampling measurements can be realized. The validity of this algorithm on the improvement of target tracking accuracy and correct associate probability is illustrated through Monte-Carlo simulations.