The utility model discloses an online dredging device for a small-size valve. The online dredging device is mainly formed by a high pressure air bottle, a first pressure adjusting valve, a first emptying valve, a first insulating valve, a pressure meter, a second insulating valve and a dredging pipeline, wherein the first insulating valve, the pressure meter, the second insulating valve, the first emptying valve and the first pressure adjusting valve are sequentially in series connection to the dredging pipeline, one end of the dredging pipeline is connected with the high pressure air bottle, and the other end of the dredging pipeline is connected with a valve to be dredged. A second emptying valve and a second pressure adjusting valve are further arranged on the dredging pipeline. By means of the structure, the online dredging device can clean up plug articles like oil sludge accumulating in the valve and recovers functions of the valve in the situation without affecting normal production. Furthermore, normal work of a pressure transmitter connected with the valve can be guaranteed. When the valve is plugged to generate unstable pressure or large difference from the actual pressure, the situations of alarm caused by error operation of a pressure detecting instrument connected with the valve and accident shutdown of the pressure detecting instrument are caused. According to the online dredging device, the situations can be avoided.