Abstract: To investigate the effects of dietary supplementation of synthetic astaxanthin on ovarian development, coloration and antioxidant capacity of adult female Chinese mitten crab (Eriocheir sinensis), three isonitrogenous and isolipidic fattening diets with 42% crude protein and 16% crude lipid were formulated by adding 0, 130 and 260 mg/kg synthetic astaxanthin (named as Diet 1, Diet 2, and Diet 3, respectively), and commercial fattening diet was used (named as Diet 4). Each diet was fed to triplicate tanks with 12 female crabs per tank for 60-day fattening. The results showed that dietary supplementation of synthetic astaxanthin had no significant effect on the hepatosomatic index (HSI) and gonadosomatic index (GSI) of adult female E. sinensis (P>0.05). Diet 3 treatment had the highest contents of carotenoid and redness value (a), and Diet 1 group had the highest lightness value (L) and yellow value (b) in the ovaries. The highest and the lowest b value of carapace were found in Diet 2 and Diet 1 treatments, respectively (P<0.05). Diet 1 group had the highest activity of peroxidase (POD) in the serum. The activities of catalase (CAT), glutathione reductase (GR), lactic dehydrogenase (LDH), total antioxidant capacity (T-AOC) and the contents of malondialdehyde (MDA) and lactic acid (LD) in serum from Diet 4 group were significantly higher than those of other groups (P<0.05). The highest and lowest activities of superoxide dismutase (SOD), T-AOC, glutathione peroxidase (GSH-Px) and GR in hepatopancreas were found in Diet 1 treatment and Diet 2 treatment, respectively (P<0.05). The activity of acid phosphatase (ACP) and hemocyanin (Hc) content in the serum from Diet 2 treatment were signifi-cantly higher than those of other treatments (P<0.05). The highest activities of alkaline phosphatase (ALP) and γ-glutamyl transpeptidase (γ-GT), and nitric oxide (NO) content were found in Diet 4 treatment. The highest activities of ACP, ALP and γ-GT in the hepatopancreas were shown in Diet 1 group. In conclusion, dietary supplementation of synthetic astaxanthin did not significantly affect the ovarian development of adult female crabs, but could enhance content of carotenoid, coloration and antioxidant capacity. These results suggest that the appropriate content of synthetic astaxanthin in the fattening diet is 90 mg/kg for female E. sinensis.