YGa43H/Y type high sensitivity high flow steam pressure reducing valve belongs to pilot operated piston pressure reducing valve. It is composed of two parts: main valve and pilot valve. The main valve is mainly composed of valve seat, main valve disc, piston, spring and other parts. The pilot valve is mainly composed of valve seat, valve disc, diaphragm, spring, adjusting spring and other parts. This product has been greatly improved on the basis of ordinary pressure reducing valve, increasing the piston area and changing the throttle structure. The sealing form has been changed, the overcurrent area has been increased, etc., so as to greatly improve the performance in terms of sensitivity, flow and life. YGa43H/Y type high sensitivity large flow steam pressure reducing valve is mainly used in steam pipelines, suitable for steam pipelines with large flow rate changes and large inlet pressure changes.