Instrumentation and control (I&C) technical management, including risk analysis and safety measure analysis, represents critical challenges in nuclear power plant I&C operations. To mitigate unit unexpected defects and reactor trip risks caused by insufficient I&C preparation, this paper proposes an automatic generation method for DCS signal flow diagrams in nuclear power plants based on DCS engineering documentation and design file analysis. The method integrates DCS configuration data, terminal connection relationships, and functional drawings to establish a standardized database and mapping relationships, enabling dynamic generation and visualization of signal flow diagrams. It efficiently generates multi-level signal flow diagrams with cyclic signal annotation and classification feature identification, significantly enhancing the completeness and accuracy of signal analysis. Practical applications at Fuqing Nuclear Power Plant demonstrate reduced misjudgment rates in risk analysis, validating the engineering value of this approach.