In order to improve state diagnosis accuracy of on-load tap changer(OLTC)for converter transformer, the research work of OLTC vibration signal preprocessing method is carried out. Based on the analysis of OLTC working principle and on-site noise, the OLTC vibration signal denoising method based on Wiener filter and the OLTC vibration signal stage division method based on Teager energy operator-double threshold method are proposed. In terms of noise reduction, the noise segment and the noisy signal segment are divided by the motor current signal, and the Wiener filter is constructed based on the spectral features of pure noise and noisy signal.By comparing the denoise result with original signal and result of other noise reduction methods, the effectiveness of proposed method is verified. As for division, the difference between vibration pulse and low frequency noise is amplified by the Teager energy operator. The validity of the method is verified by comparison between result of observation and proposed method. Based on the vibration signal pre-processing method proposed in this paper, high signal-to-noise ratio vibration signal and vibration stage information for OLTC state diagnosis can be provided.