对本实验室筛选的菌株苏云金杆菌ＤＬ－５７８９进行了形态观察、杀虫谱测定。发现该菌株对鳞翅目斜纹夜蛾有特异性高杀虫活性，对小菜蛾、棉铃虫也有较高杀虫活性。该菌对斜纹夜蛾的特异高杀虫活性与上清中的某种外毒素相关。对该外毒素进行了性质鉴定和提纯，确定是一种分子量为２３．４ＫＤａ的蛋白质分子 Bacillus thuringiensis strain DL-5789 screened in our laboratory was observed morphologically and insecticidally. The strain was found to have specific high insecticidal activity against Spodoptera litura and insecticidal activity against Plutella xylostella and Helicoverpa armigera. The specific high insecticidal activity of this bacterium against Spodoptera litura was associated with some exotoxin in the supernatant. The nature of the exotoxin was identified and purified, identified as a molecular weight of 23.4KDa protein molecules