The thermophilic Bacillus subtilis TT68 was optimized for β-mannanase production in the present report. The fermentation conditions,including carbon source,nitrogen source,ratio of carbon source and nitrogen source,amino acids and vitamins,were optimized in order to improve the production of β-mannanase. The optimized medium is composed of 4 g/L konjac powder as carbon source,0.7 g/L soybean meal powder,2 g/L L-valine,and 0.75 mg/L Pyridoxine hydrochloride (VB6). The highest enzyme activity of 7500 U/mL was obtained after incubation for 6 days in the optimized medium. When the strain was incubated using a 5 L fermentor for 2 days,the activity was up to 9870 U/mL. Bacillus subtilis TT 68 could produce a high yield of β-mannanase utilizing the inexpensive carbon source and nitrogen source in a short period. Thus,the strain displays a great potential for the industrial production of β-mannanase.