Abstract：Objective Clinical pharmacists studied drug interactions between rifampicin and voriconazole by therapeutic drug monitoring (TDM). Methods The drug interactions between rifampicin and voriconazole were revealed based on the monitoring of serum concentrations of voriconazole in patients with rifampicin and after the discontinuation of rifampicin. Results In 18 patients with rifampicin combined with voriconazole, the voriconazole serum concentrations of 94.44% of patients were lower than the limit of effective treatment concentration (1.0mg/L), of which 72.22% were lower than the quantitative limit of 0.16mg/L. Among the 19 cases of patients who used voriconazole after rifampin was discontinued, the variconazole serum concentrations of 12 patients were less than 1.0mg/L within six days of discontinuation, accounting for 63.16% of the total cases and 91.67% of the six-day cases. The variconazole serum concentrations of five patients were greater than 1mg/L for seven days and above after rifampicin was discontinued, accounting for 26.32% of the total cases and 83.33% of the cases of seven days and above. Conclusion Rifampicin seriously reduced the serum concentrations of voriconazole, and it is very likely that the voriconazole serum concentrations increased into the effective concentration range after discontinuation of rifampicin on the seventh day, and thus the combination of voriconazole and rifampicin should be avoided in clinical practice. With the help of TDM, clinical pharmacists successfully interfered with clinically meaningful drug interactions. TDM is an effective technique for clinical pharmacists to participate in drug therapy.