This water-using pressure reducing valve is used in various building’s water supply system, fire-fighting system, central air-conditioning system and warming systems. It is used for the pressure reduction of branch pipes so as to have the water supply pressure distributed more reasonably, to avoid over-pressure of partial water supply and optimize the water supply of high buildings. And it can replace the frequency-adjusting speed variable water pump of the quarters and the water pump of the quarters in the fire-fighting water supply system. When it is used in the household water supply system, it can protect all tape halters and other water utensils.