Abstract: This article focuses on the stability of networked control systems(NCSs) with variable sampling and time delay. NCSs are modeled as an equivalent input delay system. By introducing a novel Lyapunov functional with discontinuities,linear matrix inequality(LMI) based sufficient conditions are derived for the exponential stability of the closed-loop system. By solving these LMIs,we can find a positive constant that determines an upper bound between a sampling instant and the subsequent input update instant,which guarantees the stability of the closed-loop system. Numerical simulation examples show that this method is efficient and less conservative than existing results in the literature.