Chinese mitten crab, Eriocheir sinensis, is an important aquaculture species in China. Large amounts of adult E. sinensis appear in the market in autumn, but the prices are much higher before the National Day (Oct. 1st). To promote rational consumption and comprehensively evaluate the edible yield and quality of E. sinensis, this study used a pond-rearing experiment (planted with Elodea nuttallii) to obtain adult E. sinensis according to the ecological and healthy culture methods. Dissection and biochemical composition analyses were conducted to systematically explore the edible yield, proximate composition, and fatty acid and free amino acid contents of adult E. sinensis tissues. Regardless of gender, the hepatosomatic index (HSI) and gonadosomatic index (GSI) differed significantly between September and October (P<0.05), but there were no differences in meat yield (MY), total edible yield (TEY), or condition factor (CF) (P>0.05). The HSI value was higher in September than in October, and the values of the other indicators were higher in October. No significant different parameters (P>0.05) were obviously observed in proximate composition between September and October, but the moisture and lipids in the hepatopancreas, lipids in the gonads, and moisture and proteins in the muscles of females differed significantly (P<0.05). Proteins, lipids, and ash in the gonads and lipids in the muscles of males were also significantly different (P<0.05). As for fatty acid, one fatty acid in the hepatopancreas of adult E. sinensis differed between September and October (P<0.05), two fatty acids in the gonads differed between September and October (P<0.05), and eleven fatty acids in the muscles differed between September and October (P<0.05). As for free amino acid, only one amino acid in the gonads of adult E. sinensis differed between September and October (P<0.05), and three amino acids (Tau, Ala, Leu) differed in the male muscles (P<0.05). In summary, the GSI, MY, TEY, and CF values of adult E. sinensis were higher in October than in September, and there were some differences in proximate composition. There were small differences in the fatty acid and free amino acid contents of the gonads, but larger differences in the fatty acid contents of the muscles. Overall, the edible yield and quality of adult E. sinensis were better in October than in September, which is important for the comprehensive evaluation and rational consumption of Chinese mitten crab.