The a-amylase gene cn7a was amplified by PCR from Bacillus sp. CN7 genome DNA. The recombinant plasmid pSE380-cn7a was constructed by inserting gene cn7a into expression vector pSE380 and then transformed into Escherichia coli JM109. The purified amylase CN7A showed an optimal activity at pH 5.5?6.0 and 65°C, the Km value is 3.784 g/L taking soluble starch as substrate, and the maximum velocity was determined as 101.2 mg/(L·min). Ca ion was not required for the thermal stability of CN7A.