The invention discloses a high efficiency composite biological green insecticide and a preparation method thereof. The composite biological green insecticide is prepared from tobacco leaf, Melia azedarach oil, titanium dioxide, solanine, tea saponin, chromafenozide, garlic powder, sodium lignosulfonate and borax. The preparation method consists of: taking the raw materials in proportion, dissolving Melia azedarach oil in water to conduct full dissolution, performing cooling to room temperature, adding borax, and conducting stirring; adding titanium dioxide, solanine, tea saponin, chromafenozide, garlic powder and sodium lignosulfonate, performing heating stirring, adding tobacco leaf, performing stirring, conducting microwave treatment, filtering, drying and grinding into powder, thus obtaining the product. The composite biological green insecticide is prepared by compounding of biological components and natural ingredients, all the effective components supplement each other and have a synergistic effect, the insecticide has obvious control efficacy on aphids, beetles and other molluscous pests, the drug efficacy can be increased according to the insect pest condition, the drug resistance problem caused by long-term use of a same agent can be avoided, the insecticide is naturally degradable, and does not leave residue on crops or bring about health problems directly.