A high-yield strain of α-amylase， named as SCUEC8 strain， was isolated from fermented straw in bovine stomach with selective culture medium to solve the problem of decomposing crop straw. The strain isolated was identified as Bacillus subtilis based on the morphological observation and physiological and biochemical characteristics combined with comparative analysis of 16S rDNA sequence. The genomic DNA of SCUEC8 strain was used as template to amplify the ba8a gene of α-amylase by PCR. The recombinant plasmid pET28a （+）-ba8a was constructed and transformed into the E. coli BL21 strain for heterologous expression to further analyze the enzymatic characteristics of Ba8a protein expressed. The results showed that the length of ba8a gene was 1 434 bp， and the molecular weight of the Ba8a protein was 52.9 ku. The relative enzyme activity of Ba8a protein was relatively high with pH 5.0 and a reaction temperature of 45 ℃. Mn²⁺ had a higher effect on promoting the enzyme activity of Ba8a protein， while Cu²⁺ had a higher effect on inhibiting the enzyme activity of Ba8a protein. Ba8a protein was relatively stable at pH 6.0 and temperature 0 ℃. It is indicated that the Bacillus subtilis SCUEC8 strain has the activity of α-amylase， which helps to improve the degradation rate of crop straw.