The invention provides an AC voltage-resistant experiment device and method used under an extreme condition, and belongs to the field of AC voltage-resistant experiment devices. The AC voltage-resistant experiment device comprises a high-temperature industrial air circulation system, a high-temperature environmental experiment chamber, a cooling system and an AC high-voltage experiment power system. In the device, 66kV high voltage is generated by employing an AC high-voltage experiment power supply, a stepped self-cooling insulation sleeve arranged externally and a core electrode arranged ina telescopic wall-through sleeve are introduced to the high-temperature environmental chamber and are connected with a tested sleeve, and the other end of the tested sleeve is connected with ground toform a complete experiment circuit. The AC voltage-resistant experiment device is suitable for AC voltage-resistant experiment requirement of a 66kV wall-through sleeve used in a high-temperature environment with 500 DEG or above.