In order to calculate the reliability of submarine pipelines under corrosion defects, the risk score and risk grade of submarine pipelines are evaluated and analyzed. Based on the failure probability model of DNV corrosion factors, the reliability of submarine pipelines is evaluated, and the reliability index and failure probability under different corrosion depths are calculated, and the safety grade is evaluated. According to the DNV-OS-F101-2007 specification, the risk factors and risk score of submarine pipelines are identified. The risk assessment process of submarine pipelines is given, and the risk score and risk grade of pipelines are determined. It can provide reference for risk assessment of high pressure gas pipeline transmission by submarine corrosion pipelines.