Abstract: OBJECTIVE To develop a derivative GC-NPD method for the determination of agmatine in rat plasma and to study its pharmacokinetics in rats. METHODS GC-NPD analysis method was used to determine agmatine in rat plasma after derivative with HFAA. RESULTS The calibration curve of agmatine in rat plasma was linear (r=0.998 0) in the range of 0.1- 50 μg·mL^-1. The lowest detectable concentration was 0.1 μg·mL^-1. The recoveries at the concentration of 0.2, 2 and 5 μg·mL^-1 were 87.7%, 90.7%, 101%, respectively. The inter- and intra-day RSDs were all less than 12%. Pharmacokinetics parameters of agmatine in rats after i.g were fit to the two-comparment model. Fitting with the two-comparment model, the pharmacokinetics parameters of agmatine in rats after ig showed that the half-life of agmatine was 109 minutes, tmax was 26 min, Cmax was 1.91 μg·mL^-1, and AUC_0-300 min was 145 μg·min·mL^-1, respectively. CONCLUSION This method is proved to be precise and reliable enough to be applied to the pharmacokinetics studies of agmatine in rats via i.g.