Abstract: Objective: To investigate the chemoresistance of human leukemia multidrug resistant cell line HL60/ADM and the reversal effect of CsA. Methods: MTT assay was used to evaluate chemoresistance and CsA s reversal effects. Accumulation of DNR was evaluated by flow cytometry （FCM）. Results: HL60/ADM is cross resistant to DNR、ADM、VCR、Har、VP 16 and MIT, but not to Acla and Ara-c. CsA increases the intracellular DNR accumulation of HL60/ADM, but not to sensitive cell line HL60. Conclusion: HL60/ADM cell line is resistance to eight chemodrugs. But to Acla, the resistance is very small. This indicates that Acla may become one of the most important drugs in treating leukemia and overcoming the multidrug resistance. CsA can reverse the chemoresistance of HL60/ADM, so it is the important reversal agent of multidrug resistance.