The fault detection and time domain optimization problems for networked switched control systems with unknown short time delays, dropouts and uncertainties are studied. Firstly, an observer-based residual generator is constructed and the stability of the fault detection system is analyzed by combining Lyapunov function and average dwell time technique. The solutions of the fault detection filters are obtained by solving linear matrix inequalities. Then, a post filter is designed to improve the performance of the fault detection system, and the optimal solution is derived by using parity space approach. Finally, a kind of adaptive threshold is developed. Simulation results show the effectiveness of the proposed method.