Xanthan gum is one of the most important commercial bio-polymers that are used in many industries due to its rheological properties. The gum generally is produced by the Xanthomonas Campestris bacterium. Using an inexpensive substrate to reduce production costs has been considered always in xanthan production process. In recent years due to an increase in environmental pollution whole attitudes are gone toward renewable energy. As appropriate structure of lignocellulosic biomasses, they are one of the most important resources to secure substrate for use in the renewable energy sector. Components of lignocellulosic materials include cellulose, lignin, and hemicellulose. Lignocellulosic materials exist in agricultural wastes, forests and meadows. Large quantities of these materials are burned annually. Rice straw as a lignocellulosic material due to high silica contents is not useable and can’t use as livestock feed therefore is burned by farmers and causes environmental pollution. On the other hand, the most important nutrient in the production of xanthan gum by Xanthomonas campestris microorganism is glucose that is supplied by sucrose and inverted sugar. Therefore, if the cellulose in rice straw is separated and converted to glucose, the primary costs of substrate will reduce dramatically and will prevent the increase of environmental pollution. In this study rice straw was used as an abundant and inexpensive substrate in the microbial production of xanthan gum. Initially the rice straw was pretreated by 8% NaOH at temperatures of 0 and 100 °C and at 0, 30, 60, 90, 120 and 150 minutes. In another part of the project pretreatment was performed by sodium carbonate at temperatures of 120, 150 and 180 °C and at concentrations of 0.25, 0.5 and 1 M. In the following the pretreated straw was hydrolyzed by cellulose and Beta Glucosidase enzymes with enzymatic activity of 45 FPU/ml and 147 IU/ml respectively. The amount of released glucose was measured by glucose kit. The maximum amount of released glucose in enzymatic hydrolysis by 8% NaOH pretreatment at 100 °C and 120 minutes and by sodium carbonate pretreatment at 180 °C and 0.5 M sodium carbonate were obtained 36.6 and 33.4 grams per liter, respectively.The biomass growth and production of xanthan charts were analyzed in order to produce xanthan. The results showed xanthan production yield from glucose was 47.5%.The maximum amount of xanthan were derived by 8% NaOH pretreatment equaled to 13.2 grams per liter at 100 °C and 120 minutes and by 0.5M sodium carbonate pretreatment equaled to 12 grams per liter at 180 °C. Key words: Pretreatment, Xanthomonas Campestris, xanthan gum, rice straw, hydrolysis