Abstract: Deepwater jacket has a typical super-large X-brace,an 8-legged structure that becomes a 4-legged structure,and a custom-designed launch truss due to the installation plan of shipment,transportation,launching and centralization. The overall rigidity of the structure decreases,and it also has characteristics such as large working water depth,harsh environment,and obvious dynamic response. By precise modeling,precise calculation of frequencies of transfer function,refinement of stress concentration factors in different regions,refinement of S-N curves in different regions,and more precise selection principles for fatigue safety factors,Miner’s cumulative fatigue damage theory is used for precise analysis of fatigue damage in the spectral fatigue analysis,which improves the structural fatigue safety of deepwater jackets.