This paper put forward Wirtinger's inequality method used to the analysis of Network control systems(NCSs) with the H ∞ performance index level based on event-driven control. Firstly, the triggering mechanism of the event is represented by a delay model. Secondly, NCSs for the coupling between the controller ,input matrix and the output matrix is eliminated by a new method . The stable condition for the closed loop system with the H ∞ performance index level can be obtained by Wirtinger's inequality and linear matrix inequalities(LMI). Finally, the validity of the filter design scheme is confirmed by a given numerical case.