Abstract: To determine the changes in residue and environmental safety of imidacloprid application on soybeans used as a vegetable,HPLC and field experimentation were conducted.At the same time,a safe application method of the insecticide was developed.The result showed that(a) the imidacloprid degradation followed first order kinetic,(b) the initial imidacloprid residue amount varies with method of application,(c) the degradation rates were basically the same,(d) the degradation coefficient,(︱k︱),was 0.186 3±0.014 9,(e) the DT50 was 3.5-3.9 d,and(f) the T99 was 22.9-26.0 d.The soybeans were sprayed with 3.00 g of effective imidacloprid per 667 m2 near time of harvest.The insecticide residues,3 days after the application,were all less than 1.0 mgkg-1,averaging 0.299 mgkg-1.When the spray was applied twice at 7d interval,the residues were all less than 1.0 mgkg-1 averaging 0.374 mgkg-1,5d after the second spray.The residue levels on the soybeans were all below the Japanese or American MRL requirements.