The invention relates to bacillus thuringiensis for preventing and controlling leptinotarsa decemlineata, and belongs to the field of the biological prevention and control of agricultural destructive pests. The bacillus thuringiensis is separated from leptinotarsa decemlineata polypides in natural environments and is identified by forms, physiological and biochemical characters and molecular biology. Cell suspension of the bacillus thuringiensis has a high pathogenic effect and insecticidal effect on the leptinotarsa decemlineata serving as invaded pests, and an environment-friendly insecticide can be produced by zymogeneous bacteria and has potential business development and application value. The optimum culture medium for the bacillus thuringiensis is a Luria-Bertani culture medium, the optimum temperature is 30 DEG C, and the optimum pH value is 7.0; under the optimal condition of the infective pathopoiesia of pathogenic bacteria, the inoculation concentration is more than 109 germs/milliliter, and after inoculation, the humidity is kept for 4 to 6 hours, and the temperature of between 28 and 30 DEG C is kept; and the pathogenic bacteria has a high pathogenic effect on 1 to 2 year-lavae of the leptinotarsa decemlineata, and a field insecticidal effect is more than doubled compared with that of the conventional bacillus thuringiensis (Bt) preparation.