Abstract: The establishment of a random vibration environment condition of an equipment mounted on a bracket is usually based on experience to be modified by the test results. The random vibration environment for spacecraft with a new configuration can only be established by tests, and the acoustic test is the only way to do that. Since there is no appropriate analysis method for such equipment to obtain the acoustic response of mounting interfaces in the initial stages of the spacecraft research, a hybrid FE-SEA method is suggested in this paper, in which the unit (with bracket) and the other part of the spacecraft are treated separately, and modeled in different subsystems. A thruster unit of Chang'E-3 is analyzed by this method, and the results are compared with the acoustic tests. It is shown that the high frequency part is obtained accurately by modeling the unit (with bracket) and the other part of the spacecraft in FE and SEA subsystem separately. Combined with the low frequency analysis, the response results can be a reference in establishing the random vibration test condition of the equipment.