Abstract: In this paper, the problem of fault detection is addressed for networked control systems (NCSs) subject to both access constraints and random packet dropout, which to the best of our knowledge has not been considered before. Both residual generation and residual evaluation as well as false alarm computation of the designated threshold are given. First, based on a deterministic formulation, residual generation is carried out in the periodic system framework. Then, residual evaluation is achieved by making full use of the stochastic properties of the random packet dropout. Finally, performance evaluation of the designated threshold, i.e., the computation of false alarm rate, is fulfilled with the assistance of Chebyshev's inequality. Simulation results are given to illustrate effectiveness of the proposed method.