The invention relates to the technical field of xanthomonas sp.SN-58 and xanthan gum production, in particular to xanthomonas sp.SN-58 and a method for preparing the xanthan gum by using the xanthomonas sp.SN-58. The method comprises strain screening. The method for preparing the xanthan gum comprises a fermentation step and a fermentation liquid extraction step, wherein during fermentation, a formula including glucose, soyabean protein and the like is adopted, and potassium chloride serving as an extraction auxiliary agent is added in a fermentation liquid extraction process to perform alcohol precipitation and extract products. The obtained xanthan gum products are applicable to milk beverage fermentation and the production of acidophilus milk and other high-protein beverages without layering and mass production with pertinence can be carried out. Thus, the conventional problems of product instability, limited application fields and the like are solved.