The invention provides an on-load tap-changer switching program online detection and diagnosis method. The method comprises the following steps that original online vibration data is detected and acquired; an enveloping curve of the original online vibration data is calculated and is defined as an original fingerprint of on-load tap-changer vibration; an original fingerprint switching program feature vector X is calculated; to-be-diagnosed online vibration data is detected and acquired; an enveloping curve of the to-be-diagnosed online vibration data is calculated and is defined as a to-be-diagnosed fingerprint of on-load tap-changer vibration; a to-be-diagnosed fingerprint switching program feature vector X is calculated; correlation coefficients A are calculated; according to the correlation coefficients A and diagnosis criteria, it is judged whether an on-load tap-changer switching program is abnormal or not. By adopting the on-load tap-changer switching program online detection anddiagnosis method, the online detection purpose is achieved.