NOVELTY - Agricultural insecticide comprises Picrin (RTM: Trichloroethylene) soluble solution having 2.5% of tobacco, and effective ingredients including (a) nicotine and oxymatrine or (b) L-albizziine, surfactant 2201, piperonyl butoxide, spreader TP, methanol, dimethylbenzene and dimethylformamide in the ratio of 0.5:20:10:10:15:27:15. The effective ingredients are extracted and separated from plants using auxiliary agent and solvent until co-toxicity coefficient reaches 172. The ratio of nicotine, oxymatrine, auxiliary agent and solvent is 2:0.5:25.5:72.    USE - The composition is useful for controlling Lepidoptera, Coleoptera and Diptera.    ADVANTAGE - The composition is environmentally-friendly as it does not cause any harmful effects to human and animals, does not cause any residue and preventive effect of 1000-2000 times which can reach higher than 95%.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for method of preparing the above-cited insecticide, which involves (1) cleaning and crushing tobacco leaf, extracting the crushed leaf twice using acidic methanol in dynamic extraction tank at 55-60 degrees C for 1 hour, vacuum filtering, and decompressing the obtained extract liquid at 45-50 degrees C until the density reaches 1.2, adjusting the obtained solution to pH of 9, extracting the obtained solution using diethyl ether, collecting and recycling the diethyl ether from the obtained product, and subjecting the obtained product to gas chromatography to obtain nicotine solution, (2) cleaning and crushing radix sophorae flavescentis or fenugreek, extracting the crushed leaf twice using acidic methanol in the dynamic extraction tank at 55-60 degrees C for 1 hour, vacuum filtering, and decompressing the obtained extract liquid at 45-50 degrees C until the density reaches 1.2, adjusting the obtained solution to pH of 9, extracting obtained product using chloroform, collecting and recycling the chloroform from obtained product, and subjecting obtained product to thin layer chromatography to obtain oxymatrine liquid, and (3) adding obtained nicotine liquid and oxymatrine liquid with L-albizziine, surfactant 2201, piperonyl butoxide, spreader TP, methanol, dimethylbenzene and dimethylformamide in the ratio of 2:0.5:0.5:20:10:10:15:27:15, and homogenizing obtained mixture at 40-50 degrees C for 0.5 hour to obtain finished product.