Abstract: OBJECTIVE To establish an UPLC-MS/MS method for the determination of 3 components as liquiritin, xanthotoxin and methylophiopogonanone A of Shashen Maidong decoction in rat plasma, and to study the pharmacokinetics of them. METHODS The choromatography was eluted with mobile phase consisted of acetonitrile and 0.1% formic acid solution at the flow rate of 0.3 mL·min^-1 by gradient elution. Multiple-reaction monitoring (MRM) scanning mode was employed for quantification with switching electrospray ion (ESI) source polarity in positive/negative mode. The pharmacokinetic parameters were calculated by using DAS 3.0 software. RESULTS The linear ranges of liquiritin, xanthotoxin and methylophiopogonanone A were 4.92-315.00 ng·mL^-1, 1.44-92.00 ng·mL^-1 and 0.35-22.00 ng·mL^-1, respectively. RSDs of inta-day and inter-day were all lower than 15%, and the average recoveries were more than 76.5%. The pharmacokinetic parameters of liquiritin, xanthotoxin and methylophiopogonanone A were as follows:AUC_0-t were (718.23±185.55) ng·h·mL^-1, (22.52±7.53) ng·h·mL^-1, and (13.55±6.03) ng·h·mL^-1; t_1/2 were (3.61±2.01)h, (6.93±7.78)h and (3.51±1.92)h. CONCLUSION The method is convenient, sensitive and specific, and can be used for analysis of liquiritin, xanthotoxin and methylophiopogonanone A in vivo.