This paper is concerned with the state-feedback guaranteed cost controller design for a class of networked control systems (NCSs) with state-delay. A new model of the NCSs is provided under consideration of the network-induced delay. A sufficient condition for the existence of a guaranteed cost controller for NCSs is presented by a set of linear matrix inequalities(LMIs). A method, which can transform non-convex to the convex, is applied. Accordingly, a numerical algorithm is proposed to obtain the lower bound. Theoretical analysis through an example shows the effectiveness of the method.