Simulating biological immune mechanism to implement performance rejuvenation is a new research approach for computing grid.  This paper analyzes and compares the immune process's characteristics and computing system's rejuvenation,  sets up the logical model of system rejuvenation based on immune agent above simulates the biological immune mechanisms to monitor resource usage and diagnose performance degradation, constructs the mathematics model,  then puts forward a method to make decision for rejuvenation policy.  On the basis of above an application regarding audio-video resource transaction process system as background is studied,  a two-stage hyper-exponential model is proposed to evaluate system performance.  The results of case study indicate that this method is effective and feasible.