Objective To investigate the clinical effect of cyclosporin A(CsA) as a reversal agent associated with classical chemotheraphy to reverse multidrug resistance(MDR) in refractory acute leukemia(RAL).Methods 56 cases of RAL were divided into reversal group(CsA combined chemotherapy) and control group(classic chemotherapy) at random.Before treatment drug resistance glucoprotein(P-gp) were detected in all patients.Reversal of multidrug resistance was compared between reversal group and control group.Results P-gp was overexpressed in RAL(62.5%).The rate of complete remission was 43.33% in reversal group and the overall effective rate was 66.67%;The rate of complete remission was 52.63% and the total effective rate was 68.42% in the group overexpressed with P-gp.The rate of complete remission was 19.23% and the total effective rate was 38.46% in control group.The curative effect in revesal group was higher than that in control group and the difference was significant(P<0.05).Conclusion CsA can reverse the drug resistance of RAL.CsA associated with classic chemoscheme is valuabe to cure RAL especially in the group with overexpression of P-gp.