On-load tap changers (OLTCs) are electromechanical devices used in the voltage regulation of the electrical networks. A non-invasive monitoring method was developed using discrete wavelet transform (DWT) for condition assessment of on-load tap-changers using vibration analysis signals. The transient vibration signals emitted during a tap change are recorded and processed using spectral analysis and standards recognition techniques. The monitoring systems which detect failure during the OLTC operation are quite complexes. In order to reduce this complexity, in this work we demonstrated a new approach based on DWT analysis. The proposed technique is presented and the experimental results as well as its simulation are discussed.