Fault detection of networked control systems (NCSs) with random and unknown network-induced delay that might be larger than one sampling period is studied in this paper. First, influence caused by network-induced delay is transformed into structured modeling error, then an existent continuous time domain robust fault detection method based on reference model is extended to discrete time domain and applied to fault detec-tion of networked control systems. The proposed method can be easily implemented by Matlab LMI toolbox, and its performance is finally evaluated by a simulation example.