To investigate the phenoloxidase activity of hemocyanin from crab,Scylla serrata,and the effects of some metallic ions on it,the methods of affinity chromatography,PAGE,SDS-PAGE,Western-blot and phenoloxidase activity measurement were used.The results indicated that hemocyanin showed phenoloxidase activity without any inductor and trypsin could inhibit the activity slightly.Compared with control group,Ca2 and Cu2 could enhance its phenoloxidase activity at an enhancement rate of 281% and 273%,respectively;EDTA could inhibit the activation by Cu2 remarkably at an inhibitory rate of 78.5%.It is concluded that hemocyanin of Scylla serrata actually had phenoloxidase activity which was influenced by Ca2 and Cu2 .