Abstract: To simulate a spacecraft on orbit with a free boundary, a micro-vibration test fixture with a large bearing capacity and a low stiffness should be established for the micro-vibration test. A simplified combination model for analyzing the micro-vibration fixture is presented in this paper. The modal analysis with consideration of the initial deformation is made to obtain the frequency characteristics of the assembly. The testing result of a typical satellite micro-vibration test fixture is used for comparison. The comparison between the analysis model and the testing results shows a 0.3% error for the sixth order frequency evaluation.