Compounded biological insecticide of pyrethrin and acillus thuringiensis and application of compounded biological insecticide

The invention provides compounded biological insecticide of pyrethrin and acillus thuringiensis and application of the compounded biological insecticide. The compounded biological insecticide consists of the pyrethrin and the acillus thuringiensis, wherein the mass ratio of the pyrethrin to the acillus thuringiensis is 1: (1-40). The compounded biological insecticide can be used for preventing and treating lepidoptera pests on brassicaceous vegetable crops. After being compounded, the pyrethrin and the acillus thuringiensis has the synergistic insecticidal activity for plutella xylostella larvae, the insecticidal effect can be remarkably improved, the medicine cost and the labor cost are lowered, and within a certain compounding ratio, a synergistic function on the insecticidal activity for the plutella xylostella larvae is achieved.