Abstract: This study was conducted to investigate the effect of different polysaccharides on non-specific immune responses in Amur sturgeons (Acipenser schrenki). Four polysaeeharides (chitosan, stachyose, yeast polysaccharide and Iipopolysac-charide) in rice bran extract (LPSR) were injected intra-peritoneally into Amur sturgeons. After 9 days, α-naphthyl ace-tate esterase (ANAE) positivity in peripheral blood, bacteriolytic and hemolytic activities were measured. The results showed that among four polysaccharides, chitosan was the most effective immunostimulator, with significant increase in all three immune parameters compared to the control. The ANAE positivity and lysozyme activity were higher than those in oth-er treatment groups. Stachyose, yeast polysaccharide and LPS showed no significant improvement in ANAE activities and bacteriolytic activities, but all displayed higher hemolytic activity than the control.