Three sizes of female Eriocheir sinensis were studied [ first-grade crab (120±5.00 g), second-grade crab (100±5.00 g), and third-grade crab (80±5.00 g) ]. The body meat lipid content and fatty acid composition of Eriocheir sinensis in different hoarding stages were studied by Soxhlet extraction method and gas chromatography. The results showed that the body meat lipid content of the three sizes of Chinese mitten crabs in the hoarding stages was lower than that of the control group. In the maintenance stage, the lipid content of body meat in the third-grade crab decreased; the second-grade crab lipid content decreased first and then increased, and reached the maximum in the third stage; the crab lipid content in the first-stage decreased first and then rose, and is the biggest in the second stage. The three sizes of Chinese mitten crabs were the lowest in the fourth stage (the second and third-grade crabs (14~22 species); the first-grade crabs (10~23 species)). The saturated fatty acids (SFA) were mainly palmitic acid (C16:0) and stearic acid (C18:0); the highest content of monounsaturated fatty acids (MUFA) was oleic acid (C18:1), followed by palmitoleicacid (C16:1); the fatty acid content of C18:2ω6, C20:5ω3 (EPA) and C22:6ω3 (DHA) in polyunsaturated fatty acids (PUFA) was dominant. The ω3/ω6 ratio recommended by FAO/WHO and EPA+DHA value are used as evaluation indexes. The three sizes of Chinese mitten crabs body meat are most suitable for consumption in the second stage, and the first-grade crab is more beneficial to human health. Taking the content of oleic acid as the nutritional quality evaluation index, the Chinese mitten crab in the second stage has good nutritional quality.