Abstract: With the rapid development of artificial intelligence technology, multimodal large models and digital twin technology provide new technological paths for intelligent operation and maintenance of EMU. This paper aimed to address the many problems faced by on-board mechanics in the daily operations of EMU. By combining multimodal large models and digital twin technology, the paper designed EMU "digital mechanic" application to assist on-board mechanics in fulfilling their job responsibilities, improve the level of intelligent operation and maintenance of EMU, and ensure driving safety. It implemented vertical adaptation of multimodal large models in the field of EMU operation and maintenance through technologies such as retrieval augmented generation, cloud edge collaborative computing, and digital twinning, helped to transform the EMU operation and maintenance mode towards digitalization.