The invention relates to a valve mechanism of a switch cabinet, comprising a middle clapboard, fixed pulleys, ropes, upper and lower valves and lower valve operating mechanisms which are fixedly arranged on cabinets at the left and right sides of the middle clapboard and are connected with the lower valve, wherein each lower valve operating mechanism comprises a master connecting rod with one end rotatably arranged on the cabinet at the left or right side of the middle clapboard, a resetting device which is arranged between the cabinet and the master connecting rod and realizes resetting of the master connecting rod driven by external force to rotate, a handcart force applied portion which is arranged on the master connecting rod and is used for a push board of the handcart to apply force to the master connecting rod so as to drive the master connecting rod to rotate, and a slave connecting rod with one end hinged with one end of the lower valve at the same side and the other end hinged with the other end of the master connecting rod; and driven by the master connecting rod, the slave connecting rod drives the lower valve to move up and down. The valve mechanism has simple structure, long service life and good synchronicity.