Abstract: For the networked control system(NCS) with time-varying bounded sampling period and time delay,it is modeled as a class of discrete dynamic interval system.Based on this,the guaranteed cost control of the system with a given quadratic cost function is studied.A design method for the optimal guaranteed cost controller is proposed in terms of linear matrix inequalities(LMIs).With the LMI toolbox,it is very convenient to solve the problems.Simulation result shows the validity of the method.