The invention provides a transformer casing pipe oil supplementing device, and belongs to the technical field of power overhauling. The device comprises a ladder body, a box body, an oil supplementingoperator and a lifting mechanism; the box body and the ladder body are in sliding cit, an oil tank and an oil pump are arranged in the box body, and one end of the oil supplementing operator communicates with an outlet of the oil pump. According to the transformer casing pipe oil supplementing device, the ladder body is moved to a transformer, the lifting mechanism is started to enabling the boxbody to upwards slide to the high position in the ladder body, a worker climbs the ladder body, the oil supplementing operator is handheld, and is connected with an inlet of the transformer casing pipe, finally, the oil pump is started to enable the oil in the oil tank to be supplemented into the transformer casing pipe, through the manner, a worker does not need to specially climb on a transformer supporting frame and only needs to climb the ladder body, work efficiency is improved, the casing pipe oil supplementing device can be away from the high-voltage wire on the transformer, and the potential safety hazard is removed.