Abstract: Bacillus subtilis is an important bacterial strain for mesophilic α-amylase.In this paper, the optimization of fermentation technology of mesophilic α-amylase by Bacillus subtilis ZJF-1A5 was studied.The parameters, such as inoculation amount, culture temperature, dissolved oxygen, pH, and culture time were optimized. Furthermore, growth curve and α-amylase activity of B.subtilis ZJF-1A5 under the optimized parameters were researched.The results showed that the optimum parameters for production mesophilic α-amylase by Bacillus subtilis ZJF-1A5 were as follows:The carbon source was the dextrin which DE value was 18, and inoculation amount of B.subtilis ZJF-1A5 was 4%, temperature 37℃, pH5.0, rotation speed 210r /min and the culture time 54h. Under above conditions, the properties of growth and producing enzyme of B.subtilis ZJF-1A5 was further studied, and exponential phase was 9¹5h, stationary phase was 15⁴8h, decline phase was after 48h.After 54h, the α-amylase activity reached a maximum value.The research had important significance in theory and practice on fermentation mesophilic α-amylase by Bacillus subtilis ZJF-1A5.