YT43H/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, and the main valve is mainly composed of valve seat, disc, piston, cylinder liner and spring parts. The pilot valve is mainly composed of valve seat, valve 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, changing the throttling structure, changing the sealing form, increasing the overflow area, etc., thereby greatly improving the performance in terms of steam pipeline, flow and life. YT43H/Y type high sensitivity large flow steam pressure reducing valve is mainly used in steam pipelines, suitable for steam pipelines with large flow changes and large inlet pressure changes.