Abstract: Taking the pipeline of X42 and X100 steel grade as a research object, this paper calculates the failure pressure of corroded pipelines with five defected pipeline assessment codes ASME-B31G, modified ASME-B31G, DNV-RP-F101, BS7910, PCORRC and nonlinear finite element method.The comparison between calculated results and testing data shows that the calculation errors of ASME-B31G code are great and the distribution is not stable, and the calculated results of modified ASME-B31G code are improved in some ways, but the calculated error is still big; BS7910, DNV-RP-F101 and PCORRC codes are more appropriate for pipeline of steel grade of X60 and above, compared to calculated results of the said assessment codes, the nonlinear finite element method has small calculated error and stable distribution in range of steel grade under research.