In order to study immunoregulation role of dietarypolysaccharide and probiotics, the fish Fugu obscurus weighing （ 167.8 ? 24.4） g were randomly divided into 6 groups. The immunosuppression control group（positive control） was given an intraperitoneal dose of 8 mg? kg^- 1 body weight cyclophosphamide（Cy） every 5 days for three times and fed on the basal diet , and the normal control group（ negative control） was injected with 0.9% NaCl solution and fed on the basal diet according to the same procedure. The other 4 groups Were intraperitoneaUy injected of 8 mg?kg^-1 .body weight Cy every 5 days for three times and fed on basal diets supplemented 0.2% chitosan, 0.1% probiotics, mixture of mannan ohgosaccharide, hadde and probiotics, mixture of chitosan and probiotics for 30 d respectively. The number of white cells in peripfieral blood, phagocytic percentage of the peripheral blood leucocytes, activity of lysozyme in hepatopanereas, proliferation responses of T and B lymphocytes from spleen and head kidney stimulated by PHA and LPS, IgM and IFN-α content from super-natants generated from spleen and bead kidney cultivated in vitro were determined. The dose of 8 mg?kg^-1 body weight Cy depressed the non-specific immunity of the fish, and all the above four immunoenhaneers had potential immunomodulationg role on the immunodepressed, fish. During the period of test, every immunity parameter examined could return to the level between depressed level and normal level or to the normal level, even exceeding the normal level. It seemed likely that different immunoenhancers may have different ways in stimulating immune organs, immune cells or immune molecules, and same immunoenhancer may also have different effects upon different immune organs, different immune cells and immune molecules. Nevertheless, according to the overall effect, the.mixture of mannan ollgosaccharide had the least immunomodulatory effect among the four immunoenhancers.