Abstract: The traditional hydro-generator unit maintenance training method has problems such as low efficiency, long period, and certain dangers in field teaching, and its training effect is difficult to guarantee. Therefore, a virtual reality-based three-dimensional visual training method and training platform for the maintenance, disassembly, and assembly of hydro-generator units are proposed. This method takes the Francis turbine-generator unit of the Three Gorges Hydropower Station as the simulation object, uses 3dsMax to create the component-level three-dimensional maintenance model, and constructs the interactive scene of three-dimensional visual maintenance, disassembly, and assembly based on Unity3D. It designs and implements the functions of a three-dimensional visual display of maintenance process knowledge, the interactive practical operation of maintenance, disassembly and assembly, and online scoring of maintenance skill assessment. It solves the problem of accuracy evaluation of uncertain maintenance steps through the AHP-fuzzy comprehensive evaluation method and physical space constraints of maintenance components and constructs a complete closed-loop of independent learning for the maintenance training of hydro-generator units. The practical application shows that the platform satisfies the requirements of maintenance training of hydro-generator units and provides effective technical support for large-scale standardized maintenance of hydro-generator units.