Abstract: Hemicellulose could be hydrolyzed adequately when wheat straw was retained in the system of formic acid/hydrochloric acid for 0.5 h under 65℃. Straw hydrolysate was fermented by Candida tropicalis to produce xylitol. The effects of different concentration of formic acid and formate on the fermentation of D-xylose were studied. D-xylose could be fermented to produce xylitol availably with a concentration of 2 g/L formic acid or 5 g/L formate. A high concentration of formic acid or formate restrained the fermentation of D-xylose. Straw formic acid hydrolysate could be fermented to produce xylitol after the formate was removed by ion exchange resins of D311. All xylose was consumed within 72 h with a xylitol yield of 16.88%(xylitol/xylose).