Abstract：Based on the experimental investigation of structure-borne sound transmission through double cylindrical shell, the blocking mass composite brace structure is summed up. The influences of blocking mass cross-section size and layout location to composite brace structure’s isolation performance are discussed through the vibration and sound radiation numerical experiment of power cabin. Vibration test of large scale power cabin modal is carried out in order to verify the vibration isolation performance of blocking mass composite brace. The result shows that the power cabin’s vibration and sound radiation is obviously reduced by blocking mass composite brace in middle and high frequency, the outer shell’s vibration acceleration level is reduced more than 3dB.