: In present project, potato wastes were used as substrate for microbial xanthan gum production. The main step in preparing lignocellulosic substrates for high yield xanthan gum production was pretreatment process. Therefore, organosolv pretreatment was performed at different temperatures of 120, 140, and 180°C, with 50% and 75% v/v of ethanol at the present and absence of 1% w/w sulfuric acid. The solid phase of pretreatment stage, was applied for xanthan gum production through the separate enzymatic hydrolysis and fermentation by Xanthomonas campestries . The results showed that under the best conditions (pretreatment at 180°C with 50% ethanol and 1% acid), xanthan gum can be produced from combination of stem and leaves with the yield of 8.3 g/l, while only 4.1 g/l xanthan gum produced from raw substrate. The organosolv pretreatment of peel wastes at 180°C with 75% ethanol assisted by catalyst, resulted in the highest xanthan production yield of 12.9 g/l, whereas, the raw peel waste produced 9.0 g/l xanthan gum. In addition, subjecting the tuber wastes to the separate hydrolysis and fermentation process, resulted 9.1 g/l xanthan gum. In order to compare produced xanthan gum with commercial sample, Fourier-transform infrared spectroscopy and thermogravimetric analysis were conducted. The comparison indicated that the quality of produced and that of commercial xanthan gum are close to each other. Keywords: Potato wates, Organosolv pretreatment, xanthomonas campestris , Enzymatic hydrolysis, Fermentation, Xanthan gum