This paper is concerned with the design problem of networked control systems with partly unknown transition probabilities. Firstly, a new time-delay switched linear system model is proposed for NCSs, in which both the network-induced delay and the packet dropouts are taken into account. A developed packet dropouts dependent Lyapunov functional is used to obtain the stability criteria, in which the method for treating the uncertainties of partly unknown transition probabilities is embedded. Furthermore, the state feedback controller can be designed. Moreover, because the partly unknown transition probabilities in our study do not need any bounds or structures of uncertainties, the obtained stability criteria can expand to the case that the time-delay switched linear system model under arbitrary switching. Finally, numerical example and simulation is used to illustrate the developed theory.