Abstract: The accurate calculation of photon transport within reactor cores is crucial for understanding phenomena such as photon heat release and the operation of self-powered detectors. This study aims to develop a high-fidelity photon transport calculation module integrated into the deterministic numerical reactor program NECP-X, enabling high-resolution photon transport simulations. The research focuses on leveraging advanced nuclear data and transport methods to achieve precise photon flux distributions and energy group structures, which are essential for reactor design and safety analysis. The method employed in this study was based on the ENDF/B-Ⅶ nuclear database, from which a multi-group photon database was generated using the nuclear data processing program NECP-Atlas. The photon transport equation was solved using a 2D/1D (two-dimension/one-dimension) transport method, which combines the advantages of two-dimensional and one-dimensional approaches to enhance computational efficiency and accuracy. This method allowed for detailed modeling of complex reactor geometries while maintaining computational feasibility. The developed photon transport module was implemented within the NECP-X framework, a high-fidelity numerical reactor program, to facilitate detailed photon transport calculations. Validation of the module was conducted at both the pin and assembly levels, with results compared against those obtained from the Monte Carlo method, a widely accepted benchmark for such calculations. The results demonstrate excellent agreement between the NECP-X photon transport module and the Monte Carlo program. The photon energy group structure and pin flux distribution obtained from the NECP-X module exhibit high accuracy, confirming the reliability of the developed method. The effective multiplication factor bias is no more than 100 pcm, indicating a high level of precision in the calculations. The radial photon flux distribution bias is within 1%, and the axial flux distribution bias is around 3.5%, further validating the accuracy of the 2D/1D transport method. These findings highlight the capability of the 2D/1D transport method to provide precise photon transport solutions, even in complex reactor geometries. In conclusion, this study successfully develops and validates a high-fidelity photon transport calculation module within the NECP-X program. The integration of the 2D/1D transport method and the use of the ENDF/B-Ⅶ database ensure accurate and efficient photon transport simulations. This work provides a valuable tool for reactor physicists and engineers, enabling high-resolution photon transport calculations that are important for reactor design, safety analysis, and the optimization of photon-related phenomena in nuclear reactors. The developed module is expected to contribute significantly to advancements in reactor physics and the broader field of nuclear engineering, offering a reliable and efficient solution for photon transport calculations in complex reactor systems.