Abstract: Addition of oligosaccharide prebiotics into feeds can effectively enhance growth and immune-related performance of fish. Alginate oligosaccharide, an oligosaccharide prebiotic extracted from marine fucoidan, plays an important role in improving growth and immune performance of aquaculture animals. In order to investigate the effects of alginate oligosaccharide on the growth and immune performance of Lateolabrax maculatus juvenile, we conducted a 42-day experiment by adding alginate oligosaccharide to basic feed at doses of 0, 50, 100, and 200 mg·kg⁻¹ (Alginate oligosaccharide: basic feed) to prepare experimental feed. The results show that the highest weight gain rate (WGR) (96.50±7.95)% and specific growth rate (SGR) (1.73±0.09)%·d⁻¹ of juvenile were observed with alginate oligosaccharide addition of 100 mg·kg⁻¹. Expression of gh was significantly up-regulated in 100 mg·kg⁻¹ group (P<0.05). Meanwhile, the intestinal muscular thickness, villus height, villus width of juveniles, as well as the activities of trypsin (TRY), amylase (AMS) and lipase (LPS) in 100 mg·kg⁻¹ group were still higher than those of the control group (P<0.05). With increase of alginate oligosaccharide content, the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) and lysozyme (LZM) all increased significantly in liver of juvenile (P<0.05), while the malondialdehyde (MDA) content decreased significantly (P<0.05). Therefore, alginate oligosaccharide can improve the immune level of L. maculatus juvenile significantly. Besides, it has a certain promotion effect on its growth. The study provides theoretical references for the use of alginate oligosaccharide to promote the healthy growth of L. maculatus.