The invention discloses a portable transformer oiling device which comprises a vertical steel pipe and a transverse steel pipe connected with the vertical steel pipe through a bent pipe. The upper end of the vertical steel pipe is connected with a transparent plastic pipe extending upward, the vertical steel pipe is further connected with an oiling pipe connector through a valve, and the end portion of the transverse steel pipe is provided with a flange for being connected with an oil inlet pipe of a transformer oil tank. In a state that the flange is connected with the oil inlet pipe of the transformer oil tank, the transparent plastic pipe is higher than a high-pressure sleeve of a transformer. The portable transformer oiling device is simple in structure and small in volume, and dismounting of the portable transformer oiling device on the transformer oil tank is convenient compared with expansion tank dismounting. The oiling of the transformer oil tank can be directly performed on the ground through the device and is convenient, and the oiling situation can be directly observed through the transparent plastic pipe in the oiling process, so that the overhaul work difficulty of the transformer can be reduced by adopting the portable transformer oiling device, and the overhaul work efficiency of the transformer can be improved.