Abstract: With the presence of random time-delay introduced by the network,the problem of H_∞ fault detection filter design for a class of networked control systems is investigated.By considering random time-delay that could be described as a Markov process,the networked control system is modeled as discrete-time,finite-dimensional Markov jump linear system.The residual generator is constructed based on this model.The corresponding fault detection problem is formulated as an H_∞ filtering problem.Through appropriate choice of the filter gain,the error between residual and fault is made as small as possible which ensure robustness of the residual against unknown inputs.A sufficient condition to solve this problem is given in terms of the linear matrix inequalities,and the filter design procedure is proposed via the cone complementarity linearization method.The numerical example shows that the proposed fault detection filter is sensitive to the fault but robust to exogenous disturbance.