Abstract: The myofibrillar proteins extracted from purple back flying squids (Symplectoteuthis oualaniensis) were glycosylated with alginate oligosaccharide, and the glycosylated protein was simulated in vitro hydrolyzed by pepsin and pancreatin. The antioxidant properties and amino acids contents were analyzed. Results show that the free amino acids concentration decreased significantly after glycosylation, which was more obvious for the first 12 h, indicating the reaction occurred between protein and saccharides. The free radical DPPH and reducing power of both protein and the in vitro digests increased after glycosylation greatly (P<0.05). Therefore, the glycosylation increased the antioxidant properties of protein. While the radical scavenging ability and reducing power decreased after hydrolysis. The SDS-PAGE indicates that glycosylated protein showed bands with greater molecule weight, and its hydrolysates had more peptides with lighter molecule weight, which suggests that the glycosylation process promoted protein hydrolysis. The essential amino acids contents decreased while hydrophobic amino acids contents increased for the glycosylated protein hydrolysates.