Abstract: Conditions of fermentation to produce extracellular xanthan gum by using Xanthomonas axonopodis FJAT-10151 were optimized to maximize quality of the gum. Single factor and orthogonal experiments on medium composition (including sources of carbon, nitrogen and inorganic ions) and fermentation conditions (including pH, time duration, fill volume and inoculum ratio) were conducted. It was found that using a medium consisting of glucose 30 g·L^-1, soybean cake powder 30 g·L^-1, and KH₂PO₄ 2 g·L^-1 at pH 9.0 with a filled culture of 50 mL containing 8% of inoculum per 250 mL flask, a yield of 21.0 g·L^-1 of xanthan gum could be obtained after fermentation for 72 h. The production capacity was 243% higher than that prior to the optimization. More importantly, a higher quality of xanthan gum with the content of pyruvic acid increased from 8.9% to 16.3% and the content of protein decreased from 15.27% to 4.8% was realized.