The invention provides a fusion system and method used between a GIM model and an IFC model, and the method comprises the steps: reading a GIM model file and an IFC model file in a power grid engineering model, and carrying out the integrity check; Respectively carrying out file analysis on the GIM model file and the IFC model file to obtain an analysis result, and storing the analysis result in aJSON or XML file form; Respectively establishing a mapping relation between the description schemes of the GIM model and the IFC model and the description scheme of the unified reference model, converting the mapping relation, and storing the mapping relation in a JSON or XML file form; Generating a plurality of spatial relationships by analyzing geometric data in the unified reference model; Andbased on multiple spatial relationships, performing difference comparison on the GIM conversion result and the IFC conversion result to obtain a version difference result. IFC and GIM models of multiple versions of one project in multiple stages of the life cycle are fused into the same unified reference model, convenience is provided for design and development of power grid projects, and the communication cost of the project is effectively saved.