Acid-hydrolyzed arabinoxylans extracted with alkali (AX1) and water (AX2) were prepared to study their effects on the immune activity and intestinal metabolites in S180 tumor-bearing mice. Chemical analysis showed that both the protein content (1.50%) and ferulic acid content (7.6 μg/g) of AX1 were lower than those of AX2 (protein, 7.97%; ferulic acid, 366.3 μg/g). The weight-average molecular weights (Mw) of AX1 and AX2 were similar and were about 3 × 104 u. Compared with the negative control group, AX samples could inhibit the tumor growth in the mice, especially AX2, whose anti-tumor capability was comparable with that of ganoderma lucidum polysaccharides (GLP). Both AX1 and AX2 could significantly increase NK cell activity in mice; AX2 had a stronger effect than AX1. Besides, AX1 and AX2 could increase the phagocytosis of intraperitoneal macrophage following intragastric administration and AX2 showed a comparable effect with that of GLP. In addition, GLP, AX1, and AX2 had significant effects on the delayed type hypersensitivity (DTH) reaction (P < 0.05) compared with the negative control group. Short-chain fatty acids (SCFA) in colon contents of mice were also detected by gas chromatography and the results showed that SCFA of the AX1 and the AX2 groups were significantly higher than those of the negative control group and the GLP group (P < 0.05).