Obscure puffer (Fugu obscurus) has economic value and aquacultural importance in China. However, it suffers from serious fish disease, particulary bacterial disease in intensive aquaculture. In spite of positive role on immune function of probiotics and chitosan, their influence on immunity and disease resistance of Fugu obscurus was unknown. Therefore, the purpose of this experiment was to ascertain the possible role of stimulating and enhancing immune response of probiotics and chitosan on obscure puffer (Fugu obscurus). Fish were separately fed on the basal diet as control or on the basal diet with various levels of chitosan(0.2%,0.5%,1.0%), probiotics (0.1%,0.2%,0.4%), chitosan plus probiotics mixture, and a mixture of mannan oligosaccharide plus probiotics for 8 weeks. The experimental fish fed on the basal diet containing 0.2% chitosan, 0.1% probiotics, the mix of chitosan plus probiotics or mannan oligosaccharide plus probiotics mix with enhanced bactericidal activity were selected to measure immunity. The results showed that T and B lymphocyte proliferation in the head kidney was promoted by feeding on the diet with the mixture of chitosan plus probiotics, while the mixture of mannan oligosaccharide plus probiotics enhanced T lymphocyte proliferation in the head kidney. Furthermore, the mixture of chitosan plus probiotics was more effective in combination than chitosan or probiotics alone according to head kidney lymphocytes proliferation and IgM content in B cell culture supernatant. IgM concentration in spleen under the treatment of LPS stimulation in all four experimental groups was higher than that of the control, however only did the mixture of chitosan plus probiotics had a significant positive effect on IgM secretion（P<0.05）. IgM level changed greatly between the control and the supplemented chitosan or probiotics group when lymphoid cells were stimulated by LPS in anterior kidney, and all the feed stuff containing chitosan or/and probiotics might result in an increase of IgM concentration（P<0.05）. However, IFN-α secretion was suppressed by chitosan or probiotics in spleen and head kidney.In the future, we need further research on relationship of several immune paremeters, immunity change before and after the tested fish are challenged by Aeromonas hydrophila (Ah) and immunoregulation of chitosan and probiotics on the fish. Key words: chitosan;probiotics;resistibility;;immunity; Fugu obscurus