Abstract: OBJECTIVE To evaluate the metabolism of compound sophora injection based on cytochrome P450s enzyme and its interaction with paclitaxel in vitro in order to provide references for clinical application. METHODS Different concentrations of compound sophora injection (v/v) were co-incubated with human liver microsomes and the substrates of CYP2C8 （paclitaxel）. After the co-incubation， 6α-OH-paclitaxel as the specific substrate metabolite was analyzed by LC-MS/MS assay and then the half maximal inhibitory concentration (IC₅₀) was calculated. RESULTS The inhibition rate of compound sophora injection on CYP2C8 was 100.0% at 0.600 g/mL and its IC₅₀ value was 0.052 8 g/mL. CONCLUSION Drug-drug interaction induced by the inhibition of CYP450 enzymes exists between compound sophora injection and paclitaxel in vitro， which can provide reference for the clinical application of these two drugs in cancer therapy.