Abstract: In order to promote the deep processing of crab products, extraction and composition profiles of fat from Portunus trituberculatus were studied. In this study, four kinds of extraction method (Soxhlet extraction, Bligh-Dyer extraction, ultrasonication extraction, and microwave extraction) and five kinds of methyl ester method (acid catalyst method, alkali catalyst method under room temperature, method of combination with acid and alkali, conventional three fluoride boron method, and one step method of three fluoride boron) were compared, and the optimum analysis method was obtained, through which the fatty acid composition of Portunus trituberculatus was analyzed. The result suggested that the best method was the application of Bligh-Dyer extraction and conventional three fluoride boron method. The results showed that twenty components fatty acids were detected by GC-MS, 9 components SFA, 4 components MUFA and 7 componets PUFA, with their percentages 42.57%, 14.91% and 42.52%, respectively. The dominated fatty acid in each category was C_16:0 (palmitic acid), C_18:1 (oleic acid) and C_22:6n3 (DHA). The ratio of n-3/n-6 polyunsaturated fatty acids (PUFAs) was 5.27, indicating that this was a n-3 PUFA-rich food. This paper showed that there was the prospect of further development and utilization of crab fat. The research might provide reference for comprehensive utilization with crab fat, and theory base for process and its industrial application.