Workshop scheduling is very important to improve the efficiency of the workshop. Intelligent scheduling can greatly improve the level of automation and intelligence of processing. However, in the traditional production process, most of the fixed man-hour data were used to estimate the operation time of the production line, while the mixed flow assembly of tractors was dominated by workers, and the operation time of workers was not fixed or even quite different. In order to meet the requirements of intelligent scheduling, it was proposed to simulate and evaluate the production plan through the digital twin workshop to enhance the interaction and feedback with the actual workshop. A digital twin 3D model scene and human-computer interaction interface consistent with the on-site tractor assembly line were built. According to the passing point information in the MES system, the real-time drive of the assembly line model was realized, and a digital twin system with strong expansibility and flexible reusability was established. The evaluation index of production plan was analyzed, and the interactive feedback between production plan management system and twin assembly line was proposed to realize the simulation operation and evaluation of production plan based on digital twin assembly line. Through the actual working hours collected by the digital twin assembly line, the production plan can be simulated and the optimized production plan can be obtained. The actual production plans of low-yield months, normal months and high-yield months within 5 days each were compared with the plans generated by the system. The results showed that the production plan obtained after the simulation evaluation of the system was superior.