The invention discloses a high-voltage and high-current composite thermally stable test method and a high-voltage and high-current composite thermally stable test device for a high-voltage casing pipe. The device comprises a high voltage generator, a high current generator, a simulating transformer tank and an insulating oil heating device which is arranged in the tank, wherein the high-voltage casing pipe to be tested is arranged on the simulating transformer tank; and the insulating oil heating device is an electric heating device which uses an externally connected power supply to heat the insulating oil in the tank to the temperature of more than or equal to 90 DEG C. The device is characterized in that the current of the high voltage generator is less than or equal to 10A, the output voltage of the high voltage generator is between 1,000kV and 2,400kV according to a test requirement, a high voltage outputting terminal of the high voltage generator is connected in parallel with two conducting rods outside the tank of the high-voltage casing pipe, and a low voltage outputting terminal of the high voltage generator is grounded; and the output voltage of the high current generator is less than or equal to 2kV, the output voltage of the high current generator is between 200A and 10,000A according to the test requirement, and an output end of the high current generator is respectively connected with two conducting rods at one end of the tank of the high-voltage casing pipe. By the method and the device, experiments which can be finished only by a large-capacity power supply in the prior art can be realized, and the test cost is greatly saved.