Xylitol may be produced with microbial fermentation technology when xylose is used as the raw material. It is important in scientific research and production fields concerned with xylose and xylitol to develop the method of separation and detection. The anionic complexes with strong UV absorption at 195 nm will form by dissolving xylose and xylitol in borax solution. They may be separated with borax buffer by use of capillary zone electrophoresis. It was shown that the resolution between xylose and xylitol gradually increased with the increase of borax concentration, but its maximum concentration was 130 mmol/L at room temperature. The resolution depended on the pH of running buffer with a maximum at pH 9.55. The resolution was independent of cetyltrimethylammonium bromide when its concentration was between 4 x 10(-6) mmol/L-8 x 10(-4) mmol/L. So the optimum conditions were as follows: borax concentration of 130 mmol/L, pH 9.55 and cetyltrimethylammonium bromide concentration of 5 x 10(-5) mmol/L in running buffer; separating voltage of -12 kV; column temperature of 25 degrees C. Xylose and xylitol could be separated on base line in 6 min under these conditions. Samples from fermentation process and the recoveries of spiked samples were determined. The relative standard deviations of the results were between 1.42%-3.11% for xylose, and 0.62%-1.32% for xylitol. The recoveries were between 96.0%-108.0% for xylose and 94.0%-109.0% for xylitol.