Six single-phase four-column transformers of 20 kVA，220 V，and short-circuit impedance of 18% （only as the body of the transformer） connected with two sets of 6-pulse rectifier bridges were regarded as 12 pulse rectifier devices to simulate the rectifier stations in the HVDC transmission system. The noise of single-phase converter transformer was measured by means of the experimental method under various conditions. Through the analysis of the experimental data，it is concluded that the higher harmonic voltage of the valve side winding is the main factor leading to the vibration and noise of the converter transformer. The shunting capacitor at the valve side was proposed to reduce high-order harmonic voltage of valve side，as well as the vibration and noise of converter transformer. The experimental results show that this proposed method is effective in noise reduction.