An extracellular?-amylase(AmyL)from a Bacillus sp WS-3L was purified 345 fold and had a recovery of 15.5%.The amylase was capable of hydrolyzing starch to yield a series of maltooligosaccharides. It was optimally active at 45℃and pH values around 6.5 and showed stability at the temperature below 40℃and pH 7.0-8.0.The amylase was inhibited by Cu~(2+)、NH_4~+、Ag~+、Hg~+ and EDTA、SDS.Michaelist constants(K_m)of the AmyL for were 2.81 mg/mL、8.37 mg/mL、1.80 mg/mL, and maximum velocity(V_(max))of the enzyme for soluble starch,amylose,amylopectin were 11.67?tmol/(min.mL)、10.00?mol/(min?mL)、13.33?mol/(min.mL)respectively.It was suggested that amylopectin is the better hydrolysis substrate for the enzyme.It was observed that the adsorption and digestion of the enzyme on different raw starches was remarkably different.Raw corn starch exhibited high adsorption of the enzyme.It was suggested that the highly stable enzyme was able to be obtained and applied very fast by corn starch chromatography.