Abstract: During the actual operations of submarine natural gas pipelines, there are many potential risks which are not conducive to the safety of the pipelines, such as third-party damages, pipeline suspensions, and pipeline displacements. Therefore, it is necessary for submarine natural gas pipelines to carry out the risk assessment, in order to identify high-risk pipeline sections and then take efficiency control measures. Based on the principle of semi-quantitative risk assessment, the risk model and evaluation indicators are studied, which is applicable to submarine natural gas pipelines, and the TWT-CEP to Ningbo terminal submarine pipeline as the target pipeline in the East China Sea. It reveals the relative risk level and relative risk ranking of the pipeline. The risk assessment results show that the overall relative risk of the pipeline is relatively small, but there are 5 sections (about 13 km) in medium risk and need a stronger risk control and management. This semi-quantitative risk assessment method has good operability and reliability, and has a practical significance for the risk ranking management of the East China Sea submarine natural gas pipelines.