Objective To study the effects of quercetin(QUE) on proliferation of rat glioma C6 cell line in vitro.Methods The cells were divided into 5 treatment groups(10,25,50,75 and 100 ?mol?L~(-1) QUE),blank control and menstruum control group.The rat C6 cells were cultivated to 1?10~6?mL~(-1) in the RPMI 1640 medium,then added into 96 holes board with various doses of QUE by 3 holes per group,and MTT assay was used to observe the proliferation of the cells treated for 24,48 and 72 h.The change of cell cycle was also observed by flow cytometry(FCM) after the cells were treated with 50 and 100 ?mol?L~(-1) QUE for 48 h.The changes of the protein P53 and Bcl-2 of C6 cells treated with 50 ?mol?L~(-1) QUE for 48 h were detected by immunocytochemical methods.(Results With) the augmentation of QUE and the extension of the treated time,the C6 cell growth was inhibited,the A values decreased and the cell number in G_0/G_l phase was increased,the cell numbers in S and G_2/M phases were cut down,and the decreased expression of Bcl-2 protein and the increased expression of P53 protein were also observed after treatment with QUE.Conclusion Inhibitory effect of QUE on C6 cell line is proved to be dependent on the treated time of the drug and the dose of QUE,and the induced apoptosis of C6 cells is implemented by the means of up-regulation of P53 protein expression and down-regulation of Bcl-2 protein expression.