As shown in Fig.3.At early stage, the δ-endotoxin grew up quickly, then changed to be steady after 48h fermentation. When the initial pH values were 3 and 11, the concentration of δ-endotoxin was relatively low, and the bacteria grewslower, these suggested that Bacillus thuringiensis could not normally grow and reproduce in strong acid or alkali environment. In weak acid environment (pH = 5), although the bacteria could reproduce, it hindered the metabolic pathways of microbial, which directly affected the accumulation of δ-endotoxin19. However, in neutral (pH = 7) or slightly alkaline environment (pH = 9), the bacteria had good physical growth, and δ-endotoxin production reached its maximum 1256 μg/ml.