The invention discloses insecticide for garden flower cultivation and a preparation method of the insecticide. The insecticide is prepared from the following raw materials in parts by weight: 16 to 25 parts of ginger, 8 to 14 parts of xanthoxylin, 6 to 11 parts of fructus toosendan, 7 to 11 parts of eucalyptus leaf camphorated oil, 3 to 5 parts of white carbon black, 4 to 7 parts of eucalyptus leaf, 2 to 6 parts of tobacco ash, 15 to 21 parts of ageratina adenophora, 7 to 12 parts of toxic ketone extract and 6 to 12 parts of hedera helix. According to the insecticide disclosed by the invention, the raw materials including the gingers, the xanthoxylin, the fructus toosendan, the eucalyptus leaf camphorated oil, the white carbon black, the eucalyptus leaves, the tobacco ash, the ageratina adenophora, the toxic ketone extract and the like are effectively proportioned to prepare the insecticide; the insecticide has high effectiveness, pertinence, environment friendliness, no secondary toxicity, no residues, no pollution, capability of keeping ecological balance and no pollution; a formula is reasonable and a preparation process is simple; the natural raw materials are adopted for preparation, so that the insecticide has no toxicity, is directly applied to flowers and has no influences on the flowers; the insecticide has a lasting pesticide effect and a good insecticidal effect, can generate the effect rapidly, and is convenient to popularize and use.