Abstract: OBJECTIVE To evaluate the in vitro antimicrobial activity of alizarin against multidrug-resistant Mycobacterium tuberculosis. METHODS The standard strains of Mycobacterium tuberculosis (H37RV) and multidrug-resistant tuberculosis (MDR-TB) strains were inoculated in different concentrations of single alizarin,alizarin combined with anti-tuberculosis western medicine, and blank control culture media of M.tuberculosis, the growth situation of M.tuberculosis was observed, and the in vitro antibacterial effect of the alizarin was evaluated. RESULTS The bacterial colonies grew normally in the model group but did not grow in the single alizarin group (80 μg/ml) at termination of culture of M.tuberculosis (H37RV) or the rifampicin group (5mg/ml).The growth of M.tuberculosis was found in the single use groups when the media resumed to be cultured for 45 days.The bacterial colonies grew in the single alizarin group (80 μg/ml) at termination of culture of MDR-TB for 30 days; the growth of bacterial colonies was not found in the alizarin (80 μg/ml) combined group; while the bacterial growth was still not found in the alizarin (80 μg/ml) combined group when the media resumed to be cultured for 45 days. CONCLUSION The alizarin shows in vitro killing and suppressing effect on M.tuberculosis (H37RV), the alizarin combined with anti-tuberculosis western medicine shows synergistic effect; it can be used as an alternative drug for treatment of drug-resistant strains infections, which needs to be further studied.