Abstract: Distributed Control System(DCS) is being applied increasingly in nuclear power plants due to its safety and reliability operation. In this paper, a new method for optimizing the reliability of the DCS design based on the sensitivity analysis is proposed. Within this method, the accident sequences after the DCS fault was firstly analyzed, and the corresponding event tree model was built. Subsequently, a sensitivity analysis model was developed to guide the DCS reliability design. Finally, a case study was performed to validate the effectiveness of the proposed method. Results indicate that the proposed DCS reliability design method exhibited superior ability in decreasing the core damage in a nuclear power plant.