Petri net models are widely used in modeling and analysis of the complex system[1]. But because of the explosion of states, it is extremely tedious and difficult for getting reachability tree in the concurrent system[2]. With the ?independence-coupling? analysis method we proposed, the traditional complicated reachability tree simple reachability tree, and the analysis procedure for concurrent system is substituted by two or more but become easier and more efficient compared with the traditional method, and the way of the transitions of system can be expressed more exactly especially for the key parts. This method was applied to analyze the example system successfully and gotten satisfied result. It can also be used to analyze other concurrent systems and the multi-thread programming.