An alkaline CMCase was partially purified from the culture medium of Bacillus sp.O74.The enzyme was purified 27.9 fold by sephadex G-100 gel filtration,ion-exchange chromatography and hydrophobic interaction chromatography.The enzyme was characterized by demonstration of optimum activity at 50℃ and pH 7.0.and its molecular weight of 52 500 determined by gel filtration.The pH range of the enzyme showing the activity is from pH 4 to 12,and at pH 9 and 10,it can keep 80% and 70% of the maximum.activity respectively.The enzyme was stable in the presence of the most metal ions, surface active agents and auxiliaries.