Abstract: Traditionally, the NPP Digital I&C mainly relies on improving the reliability to meet the safety objectives of the plant. With the improvement of regulatory requirements, based on the improvement of equipment reliability, the design method based on probability theory technology has gradually become a new research direction of the safety design for nuclear power plants. Based on the analysis and research of typical power plant initial events, this paper applied the probabilistic safety assessment (PSA) technology to carry out PSA analysis and modeling, and integrate it in the PSA model of the power plant. Through the quantity analysis results, the weak points are identified, and the optimization modification is given. On this basis, a set of reliability design process for realizing the overall safety objective of NPP Digital I&C is proposed to enhance the overall safety of nuclear power plants.