The present study was conducted to investigate the effect of yeast β-glucan (Angel Yeast Co., Ltd, Yichang, China) either by orally (in feed) and injection or β-glucan and emulsion-oil vaccine (β-AH) on the immune response and its protection against an infection of the bacterial pathogen carpio haematopterus. And 1 800 healthy with body weight of (32.33±0.21) g were selected, and randomly divided into 12 And groups (Ⅰwith 3 replicates in each group and 50 fish in each replicate. Five levels (150, 300, 450, 600 and 750 mg/kg) of β-glucan were added in the diets of ⅡⅫ groups were fed with basal diet (0 mg/kg β-glucan), respectively. On the first day (00: 00) before the experiment, three different dosages of β-glucan of 150, 450, 750 mg/kg(body weight) of fish were injected intraperitoneally to the of ⅦⅫ groups. Similar, yeast β-glucan was administrated by injection with inactive vaccine and oil emulsion for Ⅹ, Ⅺ and Ⅻ groups in three doses (1.50 g/L, 4.50 g/L7.50 g/L) respectively. On the 7 th, 14 th, 28 th, 35 th, and 42 th days of the experiment, LZM, PI and agglutinating antibody titer were determined. On days 43 and 50 the fish were selected and divided into two subgroups under each treatment group for challenge with 2×LD₅₀ concentration of and subsequently, RPS was recordedon day14 post challenge. The results showed that LZM and PI rose to their highest levels on day 35, and the highest protectionin the challenge study after feeding with the diet containing 450 mg (yeast β-glucan)(diet), however, there was no significant difference in agglutinating antibody titre of . On the contrary, the result was observed depressed those parameters in ( injected β-glucan and β-AH significant enhanced the LZM, PI, agglutinating antibody titre and RPS than control and test fish fed with diets supplemented β-glucan. The results indicated that those parameters rose to their highest levels on 35 days at a medium dose. Injection of high-dose β-glucan and β- LZM, PI, agglutinating antibody titre and RPS in 42 d gradually strengthen contrast medium. The challenge by 2×LD₅₀ result showed that the RPS was significantly increased with increasing dietary β-glucan up to 450 mg/kg (85.46±7.71, < 0.05), but there were no significant differences for β-glucan 450 mg/kg to 600 mg/kg (> 0.05), and decreased thereafter with further increases in dietary β-glucan. Compared to the dietary supplementation, does injected with β-glucan and β- had increased RPS. The best RPS of fish was obtained at 450 mg/kg or 4.50 g/L respectively. It could be concluded that the yeast β-glucan can be used as immunostimulants and enhancement of immunity and survival of the