The utility model provides single-hole vacuum oil injection equipment of an oil-immersed transformer. The device comprises a vacuum pump unit, a water-gas separator, an oil storage tank, a vacuum oilfilter unit, an oil storage tank valve and a three-way pipe, the vacuum pump group comprises at least one vacuum pump; wherein each vacuum pump is independently connected with a vacuum pump valve, thevacuum pump set is sequentially connected with the water-gas separator, the three-way pipe and the transformer check valve, the transformer oil conservator is connected with an oil conservator valve,the oil conservator valve is connected with the three-way pipe, and the oil storage tank is sequentially connected with an oil storage tank valve, a vacuum oil filter set and a transformer oil injection and discharge valve. According to the single-hole vacuum oil injection equipment of the oil-immersed transformer, oil injection is easy and convenient, and transformer oil can be prevented from being oxidized.