Abstract: Telmisartan and hydrochlorothiazide in human plasma were determined by high performance liquid chromatography-tandem mass spectrometry （HPLC-MS/MS）. Telmisartan, hydrochlorothiazide and the internal standard were extracted from plasma using V (diethyl ether)∶ V (dichloromethane)=60∶40, and separated on a Zorbax Eclipse XDB-C 18 column using acetonitrile-5 mmol/L ammonium acetate as mobile phase by gradient elution. Detection was carried out by multiple reaction monitoring (MRM) on a 3200Q-Trap LC-MS/MS system. The assay is linear over the range 1.0—1 000.0 μg/L with a lower limit of quantitation of 5.0 μg/L for telmisartan， and linear over the range 0.6—200.0 μg/L with a lower limit of quantitation of 0.6 μg/L for hydrochlorothiazide. Intra and inter-day precision are less than 15%. The relative deviations are in the range of -5.6%—4.3% for telmisartan， and -6.3%—2.7% for hydrochlorothiazide. The recoveries of telmisartan and hydrochlorothiazide are more than 50%， and stabilities are good.