The utility model discloses an air duct device and a thermal stability detection environment test device of a power capacitor, the air duct device comprises an inner wall, an outer wall and a thermalinsulation layer arranged around the inner wall, an air duct is arranged between the thermal insulation layer and the outer wall, and the air duct comprises a main circulating air duct and a jacket air duct; a switching device is arranged between the main circulating air duct and the jacket air duct; box doors are arranged on the inner wall and the outer wall; after the door on the inner wall is closed, a test space is formed in the door, and an air grid is arranged on the test space and used for ventilating with the main circulating air duct. The device is simple in structure, and the air grid is closed after a test sample reaches thermal stability; when the switching device is turned on, gas in the main circulating air duct and the jacket air duct circulates, air in the test space is ina static state, and the reliability and accuracy of the detection structure for the thermal stability test are improved.