The invention discloses a valve locking device for an armored withdrawable switch cabinet. A movable plate, a baffle and a limiting plate are horizontally placed in sequence from top to bottom. A longitudinal slotted hole I is formed in the rear protruding part of the right end of the movable plate. The limiting plate is fixed to a cabinet body, and a transverse slotted hole II is formed in the middle of the limiting plate. A round hole is formed in the middle of the baffle. A bolt I penetrates through the slotted hole I, the slotted hole II and the round hole in sequence from top to bottom. A bolt II penetrates through the front right end of the movable plate and the front right end of the limiting plate in sequence from top to bottom, so that the movable plate and the limiting plate are hinged. The rear end of a spring is fixed to the rear left end of the limiting plate, and the front end of the spring is fixed to the rear end of the rear protruding part of the movable plate. The valve locking device has the advantages of being flexible, convenient to use, safe, reliable and easy to install.