Abstract: Risks may exist in the design, construction, operation and disposal of the submarine oil and gas pipeline, which is an integral part of the offshore oil and gas field production system. To minimize all kinds of risks in the full life cycle of submarine pipeline and reduce accidents of submarine oil and gas pipeline, risk assessment was carried out based on the full life cycle management process of submarine oil and gas pipeline, and the full life cycle risk assessment system for submarine oil and gas pipelines was established. The full life cycle of submarine oil and gas pipeline was divided into 6 stages according to the time attribute of submarine oil and gas pipeline, and similarly, the pipeline was segmented by the spatial attribute based on the principle of progressive subdivision. By sorting out the constraints affecting the pipeline safety in different stages, assigning weights to the constraints, and establishing the pipeline failure possibility scoring model and failure consequence assessment model, the risk value was obtained. The risk level of the pipeline shall be determined by the risk value and will be the basis for control of hazardous pipeline sections, which will effectively improve the risk control level in the full life cycle of the pipeline and provide reference for the full life risk management of the submarine oil and gas pipeline.