OBJECTIVE： To develop a method for the determination of valsartan concentration in human plasma and urine. METHODS： Plasma sample were acidified and extracted with diethyl ether for analysis， and urine sample was diluted directly for analysis. The samples were all determined by LC-MS/MS， and the separation was performed on a Aglient ZORBAX SB-C18 column with mobile phase consisted of acetonitrile and 0.1％ formic acid （gradient elution） at flow rate of 0.2 ml/min. Ion transition was determined ESI ion source under multiple ion reaction monitoring with quantitative pair m/z 436.4→253.2 and qualitative ion pair   m/z 436.4→291.3 for valsartan， and quantitative pair m/z 423.4→207.1 and m/z 423.4→180.2 for internal standard losartan. RESULTS： The linear range of valsartan were 4-5 000 ng/ml in plasma and 20-50 000 ng/ml in urine； the limit of quantification were 4 ng/ml and 20 ng/ml； plasma extraction recovery of valsartan were 61.21％-70.30％. The variation coefficient of internal standard normalized matrix effect were 3.20％ and 11.21％. The within-day and between-day RSDs were no more than 8.34％. CONCLUSIONS： The method is proved to be rapid and sensitive， and suitable for the determination of valsartan in human plasma and urine and pharmacokinetics study.