Abstract: Microgravity experiment facility by electromagnetic launch is the frontier in the area of the ground-based microgravity simulation, but its challenge is the problem of vibration and noise caused by the motor thrust, mechanical structure irregularity and aerodynamics, which affects the microgravity level of experiment cabin. Base on the mechanics of a microgravity drop tower, we analyze the motion kinematics and dynamics, and study the vibration response of the cabin caused by the combined effects of motor thrust, rail irregularity, and aerodynamic noise. By using simulations on aerodynamics, vibration and acoustics, we get the estimated results of microgravity level of the experiment cabin. The microgravity time is about 4 seconds and the microgravity level is 10⁻⁵g for the inside-cabin. This work provides the theoretical analysis for the microgravity facility design and performance assessment.