In the process of OLTC switch, monitor and process OLTC’s drive motor current signal and switch vibration signal. Through the correlation analysis of signal and the running state of the OLTC, indexes are used to reflect the running status of OLTC significantly, and its relative quantitative values can be formed basing on the normal operation standardization. A set of indexes is a sample, and through the analysis of the correlation between the sample and a sample of normal, or through the partial correlation analysis of two samples between more than two sets of samples, the correlation coefficient and the partial correlation coefficient can be acquired. The correlation coefficient and the partial correlation coefficient are important reference indexes for evaluating OLTC running status and judging the OLTC running state change trend.