The invention discloses a preparation method of environment-friendly biological insecticide. The environment-friendly biological insecticide is composed of nicotine, derris, ammonium sulfate, monoammonium phosphate, potassium sulfate, borax, zinc sulfate, ferrous sulfate, calcium powder, a rooting agent, chicken manure, humic acid, K7 rare earth, zeolite powder, azone, chitosan, fresh ginger, herba geranii, artemisiae annuae herba, fructus cnidii, tripterygium wilfordii, radix stemonae, pod pepper, garlic, alkyl sodium sulfonate, ginkgo nut extract, pymertrozine, menthol, dimethylbenzene, cypermethrin, lemon essence and deionized water. Compared with the prior art, the preparation method of the environment-friendly biological insecticide has the advantages that plant fermentation extraction is adopted, ingredients beneficial for plant growth are adopted, and the environment-friendly biological insecticide is weak in smell and harmless to human bodies, protects the environment, kills pests, facilitates growth of plants and has the application and popularization value.