Objective To develop a liquid chromatography technique coupled with tandem mass spectrometry (LC-MS/MS) for simultaneous determination of four active catechins EGCG, ECG, EGC, and EC of tea polyphenols (TP) in rat plasma in order to further study its multi-component pharmacokinetics. Methods Following a single step liquid-liquid extraction of plasma samples with ethyl acetate, the four catechins were separated on a Hypersil ODS C18 column using an isocratic mobile phase composed of methanol-water (30︰70). The detection using a mass spectrometer was performed under negative ESI in the MRM mode. The analytes were identified by reference to both MRM and tR values and quantified using peak area internal standard method. Results The method was shown to be specific without interference from matrix, metabolites, and impurities present in TP raw material and to be sensitive with LOD and LOQ of 1.5 and 10 ng/mL (EGCG) as well as 0.75 and 5 ng/mL (ECG, EGC, and EC). A good linearity was obtained over a wide range of 10-10 000 ng/mL for EGCG and 5-5000 ng/mL for other three catechins (r > 0.996). The method was validated to be reproducible and reliable, as evidenced by intra-batch and inter-batch precision of less than 10% and 11%, accuracy of 97.13%-106.05% and 99.22%-103.14%, respectively. The recovery of extraction ranged from 72.74% to 89.13%, matrix effect from 88.76% to 105.97% for four catechins. The method was successfully used to study the pharmacokinetics of TP iv administered to rats at a dose of 100 mg/kg. Conclusion This method is shown to completely meet requirements for the multi-component pharmacokinetic study of TP in rats. Objective To develop a liquid chromatography technique coupled with tandem mass spectrometry (LC-MS / MS) for simultaneous determination of four active catechins EGCG, ECG, EGC, and EC of tea polyphenols (TP) in rat plasma in order to further study its multi -component pharmacokinetics. Methods Following a single step liquid-liquid extraction of plasma samples with ethyl acetate, the four catechins were separated on a Hypersil ODS C18 column using an isocratic mobile phase composed of methanol-water (30:70). The detection using a mass spectrometer was performed under negative ESI in the MRM mode. The analysis was identified by reference to both MRM and tR values ​​and quantified using peak area internal standard method. Results The method was shown to be specific without interference from matrix, metabolites, and available present in TP raw material and to be sensitive with LOD and LOQ of 1.5 and 10 ng / mL (EGCG) as well as 0.75 and 5 ng / mL (ECG, EGC, and EC). ed over a wide range of 10-10 000 ng / mL for EGCG and 5-5000 ng / mL for other three catechins (r> 0.996). The method was validated to be reproducible and reliable, as evidenced by intra-batch and inter The recovery of extraction ranged from 72.74% to 89.13%, the matrix effect from 88.76% to 105.97% for four catechins. The method was successfully used to study the pharmacokinetics of TP iv administered to rats at a dose of 100 mg / kg. Conclusion This method shows limited requirements for the multi-component pharmacokinetic study of TP in rats.