Nuclear power plant instrumentation and control systems are the core control systems of nuclear power plants, and their reliability directly affects the safe operation of nuclear power plants. DCS boards, as critical components of the system, can lead to severe consequences if they fail. This paper proposes a failure rate correction method based on Bayesian updating for reliability analysis of DCS boards in nuclear power plant instrumentation and control systems. By combining the failure rate provided by the MIL-HDBK-217F manual and actual operating data, a correction model is constructed to improve the accuracy of reliability analysis. This paper provides a detailed introduction to the research design, sample selection, data collection methods, and data analysis steps, and verifies the effectiveness of the correction method through an example.