Abstract: The characterization ofβ-1,4-D-mannanase producd by MSJ-5,isolated from konjac soil, was investigated.Cultivating in shake-flask at 32℃for 32 h,the enzyme activity reached the highest value and then the mount ofβ-1,4-D-mannanase peaked.In addition,the optimum conditions for the enzymatic activity are pH7.0and50℃,and it is stabilized at pH 5.0-7.0.Furthermore,Konjac mannan was efficiently hydrolyzed by the MSJ-5mannanase and its viscosity was reduced significantly,and the product was mainly a mannooligsaccharide.Our results suggest that MSJ-5has the application potential to the feed enzyme preparation and oligosaccharide industry.