In the innovative design stage of machine tool (MT), in order to understand the motion status of the MT under different conditions, shorten the development cycle, and improve machining accuracy, this paper proposes a digital twin modeling method for large crossbeam mobile gantry milling machines. By combining digital twin technology, the selection of MT motion components and the design of various motion mechanisms were completed, as well as the machining scheme design of the MT bed. Modeling and simulation were conducted to complete the workpiece machining function, By using digital twin technology to virtually simulate CNC MT and verify their properties in physical prototypes, new ideas are provided for the application of digital twin technology in the design process of CNC MT.