Abstract: To meet the dynamic balance testing requirements for large spacecraft, this paper analyzed the main influencing factors and challenges in the testing process. A comprehensive testing system, integrating a dynamic balance facility with a vacuum chamber, was proposed to achieve high-precision measurements of large, massive spacecraft under low-vacuum and low rotational speed conditions. The system leveraged sensor potential changes due to the rotational and horizontal movements of the platform, as well as the hinge swing in the testing setup, to measure static and couple unbalances. Key aspects such as mechanical interface accuracy, dynamic balance of the testing equipment, and measurement efficiency are controled to ensure high-precision testing. In a vacuum environment, the static unbalance trim accuracy and couple unbalance trim accuracy reached 3 kg·mm and 12000 kg·mm², respectively. The system is capable of testing the dynamic balance of large, irregular rotating bodies.