Since the circle error probability (CEP) of the laser gyroscope inertial navigation system (INS) based on a certain weapon control system is a little larger in ground dynamic navigation test, an effective vibration-damping system has been designed. Data processing for the vibration experiments’ results and normal mode analysis show that the resonance frequency of the original mounting board is near the mechanical dither frequency of the laser gyroscope, which can lead to a larger mounting board response at the mechanical dither frequency. This is the main reason for the larger navigation error. A stiffer mounting board was designed, and another mounting bracket with better dynamic characteristics was developed. Ground vibration experiments and navigation simulation for laser gyroscope show that the new vibration isolation system can feed the desired requirements.