Abstract: The Top Tensioned Riser (TTR) is mainly applied to single column platforms and tension leg platforms in the development of deep water oil and gas. The risks in the operation of the TTR were analyzed to guarantee the safety and reliability of ocean engineering operation. Based on the data processing and statistical analysis results of the riser failure data in the continental shelves of the United States, the risk sources were identified by conducting the HAZOP analysis on the key operating procedures of the riser. The fault tree of TTR failure was established on the basis of the causality of the risk sources, and the minimum cut set was achieved by ascending method. Integrating the analytic hierarchy process of fuzzy mathematics and experts grading method, the fault tree was analyzed quantitatively. The probabilities of occurrence of basic risk events and top events in the fault tree were determined, on the grounds of the experts grading. The problem of deficiency and high uncertainty of data is solved by identifying the risk sources in the operation of TTR and establishing a fault-tree based failure model. This research provides a reference for the risk management of deepwater risers.