Abstract: The proliferation of xylooligosaccharides (XOS) produced from enzyme hydrolysis and hightemperature degradation of xylan to Bifidobacterium adolescentis in vitro was studied. The results showed that in vitro fermentation of B.adolescentis employed 3 g/L enzymatic prepared XOS as carbon sources for 18 h, the highest cell concentration reached 0.43 g/L, and cell proliferation was more than 3.73 times than that of the initial. When B.adolescentis incubation used 3 g/L XOS which prepared from hightemperature degradation of xylan as carbon sources, the maximal cell concentration of 0.19 g/L was obtained for 24 h fermentation and 1.16 times proliferation than that of the initial. It was found that B.adolescentis could metabolize xylobiose and xylotriose preferentially, and released arabinose and xylose while consuming the XOS that DP above 3. It was shown that xylobiose, xylotriose, xyloteraose, xylopentaose, xylohexaose were consumed 94.00 %, 50.00 %, 83.87 %, 60.87 % and 48.28 % of the initial by B.adolescentis. The mainly metabolites of B.adolescentis to XOS were lactate, acetate and propionate.