The paper dealt with the proximate biochemical composition and fatty acid composition of Chinese mitten crab Eriocheir sinensis acclimated to Tibetan plateau during its overwintering by virtue of biochemical analysis.The results are as follows: (1) Hepatopancreas index (HSI) decreases significantly after overwintering, from 11.72% to 9.96%; (2) After overwintering, relative content of total lipid and protein in hepatopancreas and muscle decreases significantly, and relative content of water in hepatopancreas goes up but down in muscle significantly; Amount of saccharides showed no significant difference in both hepatopancreas and muscle during overwintering; (3) Relative content of free fatty acids and phospholipid in total lipids of hepatopancreas and muscle reduces significantly after overwintering; Relative contents of triglyceride in hepatopancreas increases but lowers in muscle significantly; (4) Among fatty acids, primary saturated fatty acids (SFA) C16:0,C16:1n7 and primary monounsaturated fatty acids (MUFA) C18:1n9 and C18:2n6 were consumed above 10% for energy metabolism during overwintering, nearly in line with SFA and MUFA burned in muscle.It was worth noting that C20:5n3(EPA) and C22:6n3(DHA)of high level in polyunsaturated fatty acid (PUFA) (23.47% and 12.38% of total lipid in muscle respectively) were also consumed, but its relative content increased to some extent after overwintering; (5) A large amount of protein in muscle and lipids in hepatopancreas are simultaneously mobilized to fuel for energy metabolism during overwintering, implying that E.sinensis cultured in Tibetan plateau is subjected to stress of both coldness and starvation.It is suggested that prior to overwintering,Chinese mitten crab acclimated to Tibetan plateau be enriched with relevant lipids and protein to improve the survival rate during its overwintering.