Abstract: Physiological and biochemical changes of Scylla serrata under low temperature condition play an important role in understanding the process of low temperature adaptat ion. In this study, Superoxi de dismutase( SOD), Catalase( CAT ) and Glutathione peroxidase( GPX) activity,malondialdehyde(MDA) content, 4 ATPase( Na+, K+-ATPase,Mg2+-ATPase, Ca2+-ATPase and Ca2+,Mg2+-ATPase) activity, as well as fatty acid composition of cell membrane in gill of S. serrata under low temperature acclimation, were determined by biochemistry methods. The results showed that, for three acclimat ion temperatures, the activity of antioxidant enzymes( SOD, CAT and GPX) increased gradually with decrease of acclimat ion temperature. Compared with the control group(27癈), SOD activity increased significantly at 5癈 and 10癈(ppppppppp<0.05). The increase of enzyme activity under low temperature indicated that there were obvious compensation effects on temperature in gills of S. serrata,which were the positive responds to adapt to the low temperature. The increment of MDA was caused by oxidant stress resulted from the accumulation of reactive oxygen species. The decrease of fatty acid saturation index was necessary for gill cell membrane to maintain and perform normal physiological function.