The invention discloses a garden pesticide and a preparation method thereof. The garden pesticide is prepared from the following raw materials in parts by weight: 16-25 parts of matrine, 8-14 parts of gynura divaricata, 6-11 parts of lycoris radiate, 7-11 parts of schoenocaulon officinale, 3-5 parts of cartap, 4-7 parts of phosphocarb, 2-6 parts of tropic ageratum herb, 15-21 parts of sodium alginate, 7-12 parts of celastrus orbiculatus and 6-12 parts of achnatherum inebrians. Due to effective matching of banlangen, gynura divaricata, lycoris radiate, schoenocaulon officinale, cartap, phosphocarb, tropic ageratum herb, sodium alginate, celastrus orbiculatus, and achnatherum inebrians, the prepared pesticide is low in raw material collection cost, simple and convenient to prepare, very good in pesticide effect on ethanol solution rice, vegetables, fruit trees, tea trees and the like and free of environment pollution, is capable of meeting environment-friendly production requirements, very well protecting seedlings and effectively killing insects, and is small in toxicity and free of influence to nursery stock or human bodies.