Aiming at improving the reliability of networked control systems, this paper first investigates the three types of redundancy methods, including dynamic, static and hybrid redundancy. A sensitivity-analysis-based reliability enhancement method is proposed for networked control systems. Using this method, the key components affecting the system reliability can be found through the reliability sensitivity analysis. The reliability sensitivity analysis result illustrates which components need to be improved first, and either static redundancy, dynamic redundancy or hybrid redundancy can be used to improve the reliability of the networked control system. Finally, a double loop networked control system is used as a case to verify the effect of our method. The static redundancy method is applied on those components which are more sensitive to the system reliability, and the system reliability is effectively improved.