Disclosed are insecticide for planting corn on north faced slopes in mountainous regions and a preparation method thereof.The insecticide comprises bean curd, three bamboo shoots, pickled vegetable strips, salt, chicken essence, sesame oil, Ceylon tea, water, evaporated milk, glutinous rice, purple rice, black rice, Semen coicis, kidney bean, lily, red bean, mung bean, lotus seed, Semen euryales, red dates, Fructus lycii, raisin, walnut kernel, almond, pulp, white sugar, Radix platycodonis, aster, Cortex mori, Radix stemona, Flos farfarae, Pericarpium trichosanthis, Radix glycyrrhizae, Folium mori, Bulbus fritillaria thunbergii, salt dark beam, jasmine peel, pear peel, Radix adenophorae, lotus root, manganese sulfate, finless eel, fish meal, corn flour, realgar wine, straw, plant ash, bean cake, organic compound fertilizer, calcium, magnesium and phosphorus fertilizer, zinc sulfate, probiotic liquid, borax, methomyl, pyridaben and omethoate.The insecticide prepared by the method is specially used for removing weed in a corn field at early stage, causes no influence on growing trend of corn, seeps into the ground after being dissolved in water and can provide nutrient to early-stage corn.