Nuclear power systems are complex multi-disciplinary systems involving thermal hydraulics, fluid mechanics, control engineering and electrical engineering. Comprehensive performance analysis and optimization of such systems require coupled multi-disciplinary modeling and simulation. Nevertheless, co-simulation via interfaces between separate single-discipline simulation software brings numerous inherent drawbacks. Hualong One is China’s domestically developed third-generation pressurized water reactor. To accelerate system modeling and simulation efficiency, this paper independently develops the unified multi-disciplinary modeling library CGN_HPR V1.0 based on Modelica and the hierarchical modeling method, with the domestic MWorks simulation platform as the core development environment. Adopting a four-tier architecture consisting of basic, component, equipment and system levels, the library supports modular, parameterized and visual modeling for streamlined simulation analysis, and addresses the technical bottleneck of insufficient deep coupling in traditional multi-disciplinary simulation workflows. Typical operating conditions of Hualong One are modeled and simulated using the proposed library, which preliminarily verifies the validity of the Modelica-based system simulation model. The results demonstrate that the Modelica-enabled simulation framework enables seamless integration of cross-disciplinary subsystems, mitigates the difficulties in multi-disciplinary coupled simulation for nuclear power plants, and improves overall system analysis and design capacity, providing key technical support for unit safety assessment and operational optimization.