The invention discloses a ground testing system for on-track micro vibration of a spacecraft, which comprises a vibration isolating foundation, a supporting truss with a framework structure, a suspended positioning platform, a gravity suspended compensation unit, an integrated control subsystem, a micro vibration measurement subsystem and a test data processing and analyzing subsystem, wherein the vibration isolating foundation is connected with the ground, the supporting truss with the framework structure is fixedly supported on the vibration isolating foundation, the suspended positioning platform is supported on the supporting truss, the gravity suspended compensation unit is hung on the suspended positioning platform, and the integrated control subsystem is used for controlling the positioning and the fixation of the suspended positioning platform via coordination of sensors in various positions and performing the overall integrated control on the state of the system. By adopting the system, the ground simulation of the on-track micro vibration environment, the measurement of micro vibration and the data processing can be realized for the spacecraft at the system level and the component level, the technical level of testing the micro vibration of the spacecraft can be improved, and the demands for testing and verification of the on-track micro vibration environment in research on the spacecraft, particularly the high-precision satellite, can be satisfied.