The invention discloses a test device for simulating spill fire and spray fire of a transformer and a method thereof. The test device comprises an oil storage tank and a transformer body. A pluralityof top openings are formed in the top of the transformer body. The top of the oil storage tank is communicated with a return pipe and the bottom of the oil storage tank is communicated with two oil pipelines including an oil injection pipeline and an oil spray pipeline; a low-pressure oil pump is mounted at one side, close to the oil storage tank body, of the oil injection pipeline and an outlet of the oil injection pipeline is communicated with a top opening; a high-pressure oil pump is installed at one side, close to the oil storage tank body, of the oil spraying pipeline; the oil spray pipeline is communicated with the top of the oil storage tank through the return pipe through the high-pressure oil pump; and an outlet of the oil spray pipeline is connected with an oil mist nozzle whichis fixed above the transformer body. The test device has advantages of diversified functions, high authenticity, simple composition, and high operability. The test device and the method thereof havethe wide application ranges and can be widely applied to a fire simulation test and fire extinguishing technology effectiveness verification of the real transformer.