The invention relates to a conversion valve used for a glass cutting machine pneumatic device. The conversion valve comprises a valve body, a suction and exhaust opening is formed in the valve body, a first pipe joint, a second pipe joint and a third pipe joint are further formed in the valve body, and the first pipe joint and the second pipe joint are symmetrically arranged on the side wall of the valve body; a rotating shaft is transversely arranged in the valve body, the two ends of the rotating shaft penetrate the side wall of the valve body, a baffle is connected to the position, located inside the valve body, on the rotating shaft, and when the rotating shaft rotates, the baffle and the first pipe joint are in shielded fit or the baffle and the second pipe joint are in shielded fit; and a pedal plate is connected to the position, located on one side of the valve body, of the rotating shaft, and the position, located on the other side of the valve body, of the rotating shaft is connected to the valve body through a tension spring. The conversion valve has the beneficial effects that the aim that one draught fan controls a glass cutting machine to perform sucking and blowing at the same time is achieved through the conversion valve, the number of pipelines of the whole machine is reduced, the structure is simple, routing is simple, assembling is convenient, and the cost is low.