The carbon dioxide pressure reducing valve is used to control the opening of the opening and closing member in the valve body to adjust the flow of the medium and reduce the pressure of the medium. Within the scope, and spray cooling water in the valve body or behind the valve to reduce the temperature of the medium, this valve is called a decompression and temperature reduction valve. The characteristic of the valve is to keep the outlet listening pressure and temperature value within a certain range when the inlet pressure keeps changing. The pressure reducing valve is an essential accessory of the pneumatic regulating valve. Its main function is to reduce the pressure of the air source and stabilize it to a fixed value, so that the regulating valve can obtain stable air source power for regulating control.