Abstract: To develop a rapid and sensitive liquid chromatography-tandem mass spectrometry(LC-MS/MS)method for the determination of endogenous glutathione in rat plasma. Glycyltyrosine was used as the internal standard(IS)and 4-(N-maleimido)phenyl trimethylammonium iodide(MPTA)was used as the derivation reagent. Chromatographic separation was achieved on a Zorbax HILIC PLUS column(4. 6 mm×100 mm, 3. 5 μm)and the mobile phase consisted of acetonitrile and 0. 1% formic acid(75 ∶25)pumped at a flow rate of 1. 0 mL/min. Detection was carried out on a triple quadrupole tandem mass spectrometer by selected reaction monitoring(SRM)in the can meet positive ion mode. The linearity ranged from 3. 000 to 2 000 ng/mL(r=0. 997 1); and the limit of detection of glutathione in rat plasma was 10 pmol/L. Matrix effect, stability, precision and accuracy of the method met the requirements. The proposed method was proved to be selective and sensitive, which is suitable for the quantification of endogenous glutathione in rat plasma.