Objective:To explore effect of 5-AZn-2'-deoxycytidine on proliferation of human lung adenocarcinoma cell line A549 in vitro.Methods:Superoxide dismutase(SOD)activity was measured by hydroxylamine colorimetric method.Inhibition effect of 5-AZn-2'deoxycytidylic acid at different concentration and different time on growth of A549 cell was determined by MTT assay.Methylene dioxyamphetamine(MDA)was measured by throbarbituric acid colorimetric method.Effect of 5-AZn-2'deoxycytidylic acid on apoptosis of A549 cell was determined by Hoechst 33258 dyeing detection.Results:5-AZn-2'deoxycytidylic acid had significant inhibition effect on proliferation of A549 cells in vitro,and the inhibition was notably dependent on time and dosage during 48-72 h;SOD level was significantly lower than those of control group(P<0.05,P<0.01),MDA level was significantly higher than those in the control group(P<0.05,P<0.01).A549 cells began to be in apoptosis after using 5-AZn-2'deoxycytidylic acid.Conclusions:5-AZn-2'deoxycytidylic acid has significant inhibition effect on growth of A549 cell,and can lead the change of lipid peroxidation.It indicates that the mechanism has relationship with A549 cell cycle tissue and induction factor of apoptosis.