The utility model discloses an on -load tapping switch, including first cavity and second cavity, second cavity upper end is provided with first cavity, is provided with the baffle between first cavity and the second cavity, setting up tapping switch in the second cavity, being provided with change over switch in the first cavity, change over switch passes through the carousel and links to each other with first transmission shaft, and first transmission shaft lower extreme is provided with first derailleur, and it is continuous rather than the second derailleur of upper end that tapping switch passes through the secondary drive axle, first derailleur lower extreme is provided with thin transmission shaft, and thin transmission shaft passes the baffle and links to each other with the second derailleur, the top is provided with ultrasonic imager, ultrasonic imager and the image processing control module electrically connected who sets up right side on first cavity in the first cavity. This novel structural design is reasonable, the probability of greatly reduced oil leak, and the moving contact that can real -time supervision change over switch and the wearing and tearing form of static contact can in time be reminded and change, make small bubble rise more easily, have improved stability and security greatly.