The purpose of this study was to explore the mechanism of CAG regimen eliminating T-cell acute lymphoblastic leukemia (T-ALL) A3 cell line and evaluate the role of G-CSF/G-CSFR system in this process. The expression levels of G-CSFR on the A3 cell membrane were detected by flow cytometry. Cell cycle changes of A3 cells treated with different concentrations of G-CSF for 48 hours were examined by propidium iodide staining method. The inhibition and apoptosis rates of A3 cells treated with various combinations of G-CSF, cytarabine (Ara-C), aclarubicin (ACR) were analyzed by Cell Counting Kit and AnnexinV Kit, respectively. The results indicated that the expression level of G-CSFR on A3 cells was 94.2%. The proportion of A3 cells in S-phase rose concomitantly with the increasing of G-CSF concentrations within 0-20 ng/ml. After incubation with Ara-C and G-CSF for 48 hours, A3 cells were inhibited more obviously compared with incubation with Ara-C alone (p<0.05, Ara-C 10(-5) mol/L and 10(-6) mol/L). After incubation with Ara-C, ACR and G-CSF for 48 hours, the apoptotic rate of A3 cells was much more than that after incubation with Ara-C and ACR. It is concluded that the expression level of G-CSFR on A3 cells is high, G-CSF/G-CSFR system has a synergetic effect on eliminating A3 cells when administrated simultaneously with chemical agents. This effect is caused through driving more cells from G0 phase into S phase, increasing sensitivity of A3 cells to chemical drugs and inducing cell apoptosis which may be one of the mechanisms of CAG regimen eliminating A3 cells.