The invention is a green pollution-free pesticide and a preparation method thereof. It is characterized in that it is obtained by mixing 78-98% of bitter kudzu whole herb extract and 1-22% of white sugar. After soaking the fresh or dry product of the whole herb of bitter kudzu, beating, squeezing the juice repeatedly 3 to 4 times, filtering, leaving the filtrate to stand still to remove starch, and concentrating to obtain the bitter kudzu extract. The green pollution-free pesticide of the present invention can kill underground black worms (in the ground during the day, and on the stems and leaves of plants at night, commonly known as cutworms), soil silkworms, earthworms, leeches in the water, red worms, and worms seen with the naked eye. The missing insects, cabbage caterpillars, aphids on plants, and plant powdery mildew, rust, downy mildew and mites (red spider, rust wall wind, scale insects) have good control and killing effects , has a killing effect on any pests that devour seedlings in the seedbed. Its insecticidal spectrum is wide, and because the plant itself is alkaline, it is easy to dissolve, so it will not remain on the plant, will not damage the soil structure, and will not pollute beneficial insects and the environment.