The utility model provides a high tension switchgear's dimension accuse device, a high tension switchgear's dimension accuse device, include: temperature sensor, microprocessor, ventilation mechanism, pressure monitoring system mechanism and gas sensor, microprocessor is according to gas sensor's detection results found high tension switchgear's state to judge whether high tension switchgear appears unusually according to the testing result of pressure monitoring system mechanism, appear when unusual at high tension switchgear that the volume of airing exhaust through regulation ventilation mechanism reduces pressure to high tension switchgear inside, microprocessor still is used for receiving the temperature that temperature sensor gathered, and when the temperature value surpassed predetermined temperature upper limit value, control ventilation mechanism was to ventilating in the high tension switchgear. Realized accurate control high tension switchgear temperature, made the high tension switchgear temperature maintain certain within range to high tension switchgear's life -span has been prolonged effectively.