The utility model relates to a device for replenishing insulating oil into an oil-filled transformer with low oil level. The device comprises an insulating oil storage tank and a high pressure gas cylinder, wherein the high pressure gas cylinder is provided with an exhaust port controlled by a pressure reducing gate valve; the lower part of the insulating oil storage tank is provided with an oil outlet controlled by a third gate valve; the upper part of the insulating oil storage tank is provided with an oil inlet controlled by a fourth gate valve. The device is characterized in that the exhaust port of the high pressure gas cylinder is connected to a gas inlet in the upper end of the insulating oil storage tank through a gas delivery hose; a first gate valve is arranged at the oil outlet of the insulating oil storage tank; the first gate valve is connected with the upper end oil inlet or the lower end oil outlet of the oil-filled transformer through an oil delivery pipe. The device is simple in structure, is convenient to operate, and can effectively meet the operation requirement of replenishing of the insulating oil into the oil-filled transformer with low oil level.