The invention discloses an insecticide, a preparation method and an application thereof, and belongs to the field of preparation technology of insecticide. The insecticide comprises the following raw materials in parts by weight: arborvitae leaves, mints, lettuces, Anabasis aphylla, paulownia leaves, Sophora alopecuroides, wormwood, ginger dioscorea, aloes, Azadirachta Indica, ash barks, flavescent sophora roots, Euphorbia soongarica, tea tree leaves, datura, pyrethrum, capsicum, sabadilla, tobacco, Chinese ash leaves, and water; the insecticide is prepared by the following steps: extraction, condensation, drying, crushing, sieving, disinfection, etc. The insecticide does not have toxic components, residuals, and pollution, and is green and environmentally friendly; the insecticide has the advantages of simple production method, low cost and good application effects; the insecticide can be used for effectively controlling blister mite, Parlatoria pergandii, long-horned beetles, chitinozoans and other plant insects, one-time killing rate reaches above 96.14%, and the insects do not have drug resistance.