The invention discloses a preparation method of efficient herbicide. The preparation method comprises the steps of drying vitex negundo,erigeron canadensis, pepper leaves and conyza canadensis in the sun, then conducting pulverization, sieving all ingredients with a 100-120-mesh sieve, conducting the drying, and obtaining first materials; adding the first materials into ethyl acetate, conducting mixing uniformly, subsequently conducting ultrasonic oscillation for extraction, conducting suction filtration and concentration, and obtaining first coarsely extracted materials; washing and drying trifolium repens roots, lilac leaves and prunus persica chrysanthemoides roots in the sun, then conducting pulverization, sieving all ingredients with a 100-120-mesh sieve, then placing all the ingredients in water, then adding a compound enzyme preparation, conducting mixing uniformly, laying the mixture for standing, conducting the enzyme deactivation, conducting suction filtration and concentration, and obtaining second coarsely extracted materials; mixing the first coarsely extracted materials and the second coarsely extracted materials uniformly, conducting the reduced pressure evaporation, and obtaining active materials; mixing the active materials, tea saponin, lemon essential oil, haloxyfop, emulsifier, dispersant, thickener, structure modifier, anti-oxidant, preservative and soybean oil uniformly, and obtaining the efficient herbicide.