This paper describes a harmless HPLC technique for detecting imidacloprid (ICP) and its metabolite, 6-chloronicotinic acid (6CA), using an isocratic 100 % water mobile phase. Chromatographic separations were performed a Daisopak® SP-200-3-C1-P with water mobile phase and a photodiode-array detector. The total run time was & LT; 6 min. The system suitability was well within the international acceptance criteria. The detection limits were 0.018 ?g/ml for ICP and 0.005 ?g/ml for 6CA, respectively. A harmless HPLC method for simultaneous detecting ICP and 6CA was developed and may be further applied to the quantification in animal-derived foods.