Aim To investigate the inhibitory and in-duction effects of the active components of SIWU de-coction on cytochrome P450 enzymes ( CYP ) and as-sess the CYP based drug interaction. Methods Ac-tive components fructose, ferulic acid, paeoniflorin, li-gustrazine and their combinations were incubated sepa-rately with human liver microsomes ( HLM) and probe substrates. Metabolites of the CYP probe substrates were determined by LC-MS/MS to assess the inhibitory activities on human CYP1 A2 , 2 B6 , 2 C9 , 2 C19 , 2 D6 and 3 A4 . Sandwich-cultured rat hepatocytes model was used to evaluate the CYP1 A2 and CYP3 A1/2 induc-tion. Results The inhibitory rates on CYP1A2, 2B6, 2 C9 and 2 C9 by the test groups at 100 μmol · L-1 were all < 62%, while the activities of CYP3 A4 and 2D6 were not affected. The CYP1A2 activities in the test groups of peoniflorin and its combinations ( 50μmol·L-1 ) were significantly enhanced, with the in-creasing fold more than 40% of positive control group. No significant induction on rat CYP3 A1/2 was ob-served for four principles and their combinations. Con-clusions The active components of SIWU decoction do not show significant inhibitory effects on six CYP isoforms. Peoniflorin could induce the CYP1A2 activity in rat hepatocytes. The induction activity is enhanced by the concomitant use of peoniflorin with ferulic acid and/or ligustrazine.