A reversed phase high performance liquid chromatographic(RP／HPLC) method was established for the determination of imidacloprid in rat plasma,which was used to investigate the imidacloprids pharmacokinetics in rats by intragastric administration.The plasma sample was extracted with methanol,then determined by RP／HPLC.The sample was separated on a C18 column(4.6 mm×250 mm,5 μm ) with a mobile phase of methanol-water(30∶70) at a flow rate of 1.0 mL·min-1,and detected at a wavelength of 245 nm.The imidacloprid concentration in plasma was detected at predetermined time intervals after SD rats were intragastrically given a single dose of lutein suspension at 68.1 mg·kg-1,then the concentration time curve was plotted and the pharmacokinetic parameters were calculated.The main parameters for intragastric administration were follows:Cmax=23.557 mg/L,tmax=7.333 h,t1/2α=4.472 h,AUC(0-t)=276.727 mg·h/L.There was a linear relationship for imidacloprid (r2=0.999 8) in the concentration range of 0.5-100 mg·L-1 with a detection limit of 10 μg·L-1.The average recovery for the analyte was 74.7%.The pharmacokinetic results in rats showed that imidacloprid was distributed in two compartment models in rats,and eliminated by the first order pharmacokinetics.The method was simple and reliable,and could satisfy the requirements for the detection of imidacloprid and its pharmacokinetic study in rat plasma.