Abstract: With the enhanced requirements of the observation accuracy and the sensitivity to the micro-vibration of the observation payload, the on-orbit free boundary condition simulation for the spacecraft in the micro-vibration ground simulation test becomes more important. A method of the low frequency elastic suspension is proposed to simulate the free boundary condition of the on-orbit satellite. And a low frequency elastic suspension device is developed based on this method, and is applied to evaluate the influence of the simulated free boundary condition on the dynamic characteristics of the satellite by the modal and frequency response analyses. The application of this device in an actual micro-vibration test of a satellite shows that the method of the low frequency elastic suspension for the satellite is reliable.