The invention discloses a long-acting insecticide against cnaphalocrocis medinalis of paddy rice, wherein the raw materials comprise the following components in parts by weight: 80-100 parts of extract of traditional Chinese medicine, 0.5-1 part of abamectin, 1-2 parts of matrine, 1-2 parts of pyrethrin, 5-8 parts of penetrant, 10-15 parts of porous starch, and 1-3 parts of surfactant; wherein thetraditional Chinese medicine raw materials of the extract of traditional Chinese medicine include tea seed cake, flaccid knotweed herb, common andrographis herb, fructus forsythiae and tobacco; the long-acting insecticide has powerful ability of killing the cnaphalocrocis medinalis of the paddy rice and long period of insecticidal efficacy without generating drug resistance and residues of pesticides.