Abstract: To explore antioxidant properties and influence on gut microbes of capsaicin and capsicum aqueous extracts, the main nutrients of capsicum aqueous extracts were determined, then taking standard of capsaicin as positive control, the antioxidant properties of capsaicin and capsicum aqueous extracts were determined. Using healthy college students' faeces as bacteria source, using 24 h anaerobic fermentation in vitro model to explore their effects on gut microbes. The results showed that the scavenging rates of DPPH free radical, superoxide anion free radical and hydroxyl free radical were 75.25%, 12.87% and 19.45%, respectively, in the range of slight spicy (0.028 g/L) to super spicy (0.112 g/L), they were lower than those of standard capsaicin. In the range of extra-spicy (0.0924~0.2918 g/L), capsaicin and capsicum aqueous extracts could increase the content of short-chain fatty acids (SCFA) in the culture system. At six hours of fermentation, capsaicin and capsicum aqueous extracts had inhibitory effects on the growth of Lactobacillus, Bifidobacterium, Clostridium, Enterobacter and the total anaerobes, but had no obvious inhibitory effects on Bacteroidetes. The capsaicin and capsicum aqueous extracts inhibited the growth of Enterobacter and promoted the growth of other bacteria at 12 h. When cultured for 24 h, they inhibited the growth of total anaerobe, clostridium and Enterobacter, and promoted the growth of Bifidobacterium, Lactobacillus and Bacteroidetes. The index PI value of prebiotics were the biggest 0.11 and 0.04 at 24 h, respectively. The B/E values were the biggest 1.60 and 1.61 at 12 h, respectively. This study would provide some data support for the research on nutrition value and health care function of pepper.