ABSTRACT As the complexity of spacecraft function has increased, the requirements for assembly quality and reliability have become more stringent. The current digital assembly simulation stays in the idealized structure and method verification, however, the spacecraft assembly process relies on manual and discrete operations, making it challenging for real time assembly quality tracing and process clarification. This paper takes the spacecraft assembly process as the research object, studies the real-time data acquisition method that fuses the acquisition node and the assembly process, and establishes the virtual-real mapping process around the central data space. A Digital twin system corresponding to the actual spacecraft assembly process was constructed based on the spacecraft assembly cell unit. The states of the manufacturing process in the physical world are fed back to the virtual space. The problems faced during assembly are reflected in real-time, and the corresponding behaviour is simulated. Based on the real-time data acquisition, real-time monitoring and numerical analysis for comparison are realized, providing a feasible solution for the application of Digital twin in the spacecraft assembly scenario.