The 97/98-21200 series pneumatic single seat regulating valve is composed of a 21200 series single seat valve and a pneumatic diaphragm multi spring actuator. The 21200 series single seat valve is a product developed based on the digestion and absorption of imported design technology. This series of single seat valves has the characteristics of large flow capacity, small leakage, large adjustable ratio, and good vibration resistance. When combined with pneumatic thin film multi spring actuators, the whole machine has a small volume and light weight. The 97/98-21200 series pneumatic single seat regulating valve has good universality and can be applied to process control of various medium and low-pressure fluids.