This project is one of the six projects of the 973 program "Safety operation and risk control of deepwater oil and gas transportation systems". Starting from the life cycle perspective, it is to reveal the combination rule and damage mechanism, failure mode of deepwater oil and gas transportation systems subject to various external loads (periodical loads, accidental loads). By considering the characteristics of each failure mode, it is to solve the system dominant failure path. By considering the typical load and structure characteristics of uncertainty, it is to provide the efficient algorithm for computing the reliability analysis of the structure characteristics of underwater. By considering all the potential damage or extreme case, the failure mode and its transmission mechanism, it is to analyze the reliability of the deepwater oil and gas transmission system. It is to provide theoretical foundation and scientific basis for the prevention and control of structure safety system of the deepwater oil and gas transmission system.