Abstract: Stability of the networked control system(NCS) with equality constraint is studied.On the assumption that the network delay changes randomly and the plant under the control of the NCS is a time-delay system with equality constraint,the NCS is modeled as a hybrid system.Then,the Lyapunov function and linear matrix inequality(LMI) methods are used to derive a sufficient condition for the asymptotical stability of the hybrid system.With this sufficient condition,by solving linear matrix inequality,the system maximum allowable network-delay and the controller at this time can be obtained easily.The numerical example and simulation are presented to demonstrate the effectiveness of the proposed design approach.