确定管道流变应力的不确定性分布是对含缺陷压力管道进行可靠性评定的前提。本文以国产常用20#钢作为研究对象，进行了材料性能及全尺寸管道的断裂试验研究，通过对管试样数据和实测材料性能数据的比较，根据对试验结果的分析比较，得出20#碳钢管道的流变应力计算式应为：（σy＋σu）／2，并且其值服从对数正态分布。 The uncertainty distribution of the flow stress in the pipeline is the precondition for the reliability assessment of the pipeline with defects. In this paper, the commonly used domestic 20 # steel as the research object, the material properties and the fracture test of full-size pipe were carried out. By comparing the data of the tube specimen and the measured material performance data, according to the analysis and comparison of the test results, The calculation formula of flow stress of carbon steel pipe should be: (σy + σu) / 2, and its value obeys logarithm normal distribution.