The invention relates to a compressed air over-pressure/ under-pressure control device, and in particular relates to a compressed air over-pressure/ under-pressure control device of an intermittent pre-expander. The compressed air over-pressure/ under-pressure control device of the intermittent pre-expander is simple in structure, can conveniently and accurately adjust the flow rate and pressure of compressed air and does not influence the product quality, and is high in working efficiency. The compressed air over-pressure/ under-pressure control device of the intermittent pre-expander comprises a first pipe body, an exhaust pipe, a first solenoid valve, a first housing, a screw, a bearing, a connecting rod, a first button, a slide rail, a slide block, first springs, etc., wherein the exhaust pipe which communicates with the inside of the first pipe body is connected to the bottom part of the first pipe body; the first solenoid valve is mounted on the exhaust pipe.