Abstract: Objective To study the effect of carboplatin on breast cancer cells and thrombopoietin（TPO） on proliferation of megalokaryocytes. Methods Effect of different TPO concentrations on megakaryocyte cell line,MO7e cells was detected by MTT assay 24,48,and 72h after MO7e cells were exposed to TPO.A proliferation curve of MO7e cells was plotted.Twenty-four and forty-eight hour inhibition rate of different carboplatin concentrations on breast cancer MDA-MB-453 cells and TPO on MO7e cells were calculated to measure and compare their half inhibition concentration（IC₅₀）. Results TPO increased the proliferation of MO7e cells in a conceetration-dependent manner and reached its plateau when at 256ng/ml.The IC₅₀ of MO7e cells was 10-fold higher than that of breast cancer cells. Conclusion TPO can promote the proliferation of megakaryocytes.The inhibitory effect of carboplatin on breast cancer cells is significantly higher than that of TPO on megakaryocytes.