Digital twin technology plays a crucial role in completing the virtual mapping of the physical workshop, enabling production monitoring and process optimization. New energy batteries are a form of green energy with advantages such as high energy density, environmental protection, and beneficial safety. The assembly line for new energy batteries is essential in efficiently obtaining battery packs of diverse varieties and high quality. This paper presents three assembly design schemes for square lithium iron phosphate battery packs as an example. By comparing the characteristics of different schemes, scheme C was selected as the preferred option for conducting three-dimensional modeling of the assembly line. This paper utilizes digital twin technology to create a digital representation of the battery pack assembly process. The process flow of the designed production line can be tested. The loading time, equipment idle time, fault time, blocking waiting time, material shortage waiting time, etc., of each workstation in the production line can be accurately calculated. Optimize the production process flow, reduce resource occupation, and save a large amount of human and material resources.