OBJECTIVE Chlorogenic acid (ChA) is proposed as one of the main bioactive compounds ofLoniceraeJaponicaeFlos (LJF).To study the pharmacokinetics and bioavailbility of ChAthat extracted from LJF following intravenous (i.v),intramuscular (i.m) and intragastrical (i.g)administration in rats by using HPLC-MC/MC.METHODS 42 rats were randomly assigned to six groups and given adose of 400 mg/kg LJF extract.Liquid-liquid extraction was used to extractanalytesfrom plasma samples with acetonitrile,then analytes were separated by linear gradient elution using methanol containing 0.01% formicacid and 0.01% formic acid as mobile phase at a flow rate of 0.4 mL/min within 4.5 min on a C18 column which temperature maintains 40 °C,using ibuprofen (IS) as internal standard.Results The specificity,linearity,extraction recovery,accuracy and stability of this method weresuccessfullyestablished.The pharmacokinetic parameters of ChA were fitted in two compartment model andcalculated by using WINNONLIN 6.1 software,partially parameters as follows: t1/2of i.v,i.m and i.g administration were 0.44,0.50 and 0.38 hrespectively,AUC0→∞ were 6931.62,6550.34 and 2591.87 ug*h/Lrespectively.The absolute bioavailability were calculated using formula F(%)=(AUCvascular/AUCi.v) x 100%,the corresponding absolute bioavailability of ChA by i.m administration was 94.50%,while by i.g administration was 37.39%.Conclusionwe found a useful HPLC-MS/MS method toquantificate ChA in rats plasma,andtheexact data about Pharmacokinetics and bioavailability of ChA(LJFextract) following different administration in ratscould provide a meaningful evidence for preparation and clinical application.