In the launching process of a spacecraft, the dynamic environment is very complex, so a vibration isolator is widely used for preventing the spacecraft from being damaged. This paper focused on a whole-spacecraft vibration isolation platform with the purpose of isolating the shock and noise transmitting directly to the spacecraft in the process of launching. The isolator is designed based on a model of circular payload adapter fitting. A voice-coil motor is designed and optimized as the active control actuator to provide proper feedback force to reduce the amplitude of the vibration, and is fixed in the whole-spacecraft vibration isolation platform, with sensors collocated on one side of the voice-coil motor in the vertical direction. The LQR control strategy is designed for the preliminary model of the isolation system in the vertical direction. Numerical simulation results are given to verify the effectiveness of the proposed isolation unit consisted of the voicecoil actuators.