Abstract: In this study,response surface methodology( RSM) was employed to optimize a fermentation medium for the production of Streptomyces althioticus LMZM in submerged fermentation with corncob as substrate. Four significant influence factors including corncob powder,soybean,yeast extract powder and magnesium sulfate were screened by the method of Plackett- Burman design. In addition,the minimum addition amount experiment was used for finding out the minimum add amount of non- significant factors to reduce the source cost. The steepest ascent design was applied to approach the optimal region of the three significant factors. And the optimal concentration and correlations among three factors were identified by central composite design. The optimal fermentation parameters for enhanced xylanase production were found to be corncob powder 27.85 g / L,soybean16.25 g / L,yeast extract powder 3.46 g / L,magnesium sulfate 1.18 g / L,potassium phosphate dibasic 0.60 g / L and disodium hydrogen phosphate 0.40 g / L.The model predicted a xylanase activity of 117.80 U / m L.After three parallel verifications,the maximum theoretic value was consistent with mean value of verification test which was 116.63 U / m L,and the xylanase production was increased by 1.28- fold in comparison with to that before optimization