本文阐述了ISO 6358-2008标准规定的表述流量特性的两个参数声速流导C和临界压力比系数b,分析阀门流量音速段和亚音速段的特性,提出临界压力比b选择的合理建议,给出了简单、方便的流量计算公式以及阀门有效截面积的计算方法。 This paper elaborates the two parameter sonic flow conductance C and critical pressure ratio coefficient b that express the flow characteristics according to the standard of ISO 6358-2008, analyzes the characteristics of valve flow velocity and subsonic velocity segment, and puts forward the reasonable suggestion of selecting the critical pressure ratio b, A simple and convenient flow calculation formula and calculation method of valve effective cross-sectional area are given.