The present invention provides a power transformation primary device constant low temperature and high-voltage test device and method. The device comprises a constant low-temperature box body, a temperature sensor, a humidity sensor, an automatic anti-interference precision medium loss measurer and a voltage regulator; the top portion of the constant low-temperature box body is provided with a high-voltage wall feed-through sleeve with a tail end located in the constant low-temperature box body, a standard capacitor connected with the automatic anti-interference precision medium loss measurerand a boosting transformer connected with the voltage regulator, and the high-voltage wall feed-through sleeve and the standard capacitor are connected with head and tail ends of the boosting transformer; the constant low-temperature box body is provided with a wiring terminal box connected with the automatic anti-interference precision medium loss measurer, and the humidity sensor and the temperature sensor are located in the constant low-temperature box body; and the constant low-temperature box body is internally provided with a current transformer connected with the high-voltage wall feed-through sleeve and the wiring terminal box. The power transformation primary device constant low temperature and high-voltage test device and method can achieve regulation and control of the humidityand the temperature in the constant low-temperature box body so as to meet most of test projects of a power transformation primary device.