Objective To explore the effect of carbon nanoparticles-epirubicin suspension on proliferation and apoptosis in human breast cancer MCF-7 cells.Methods MCF-7 cells were cultured with different concentrations of CNP-EPI in vitro.CCK-8 assay was used for determinate inhibition effect of CNP-EPI on the proliferation of MCF-7 cells at different concentration and different time.According to the determination of IC90,5 μg/ml CNP-EPI was selected,and cell morphology and cell apoptosis rates were observed after 24 h.Results The inhibition effect of the CNP-EPI was stronger significantly in CNP-EPI group than in normal control group within 24 h,48 h,72 h when the concentration was from 1 μg/ml to 200 μg/ml (P＜0.01).The inhibition of CNP-EPI on the proliferation of MCF-7 cells was gradually strengthened in a dose-dependent relation within the same time,and the inhibition effect is reduced in the same concentration of drugs with the time extension,but it still has a strong inhibitory effect in 72 h,and the inhibition effect of different concentration of CNP was not obvious on MCF-7 cells.Obvious changes of cell morphology were observed under inverted microscope such as:a lot of dead cells,cell adherent growth poor,cell morphology became round and karyopycnosis etc,in 5 μg/ml CNP-EPI group after 24 h.However,no obvious abnormity of cell norphology was observed in normal control group and corresponding CNP group.Late apoptosis rate was (14.57±2.41) ％,the mortality rate could reach (78.63±-20.55)％ in 5 μg/ml CNP-EPI group after 24 h.The mortality rate and apoptosis rate of cells was higher significantly in CNP-EPI group than in CNP group and normal control group (P＜0.05).Conclusion CNP-EPI can obviously inhibit the proliferation or kill human breast cancer MCF-7cells,and the inhibition effect of CNP-EPI on proliferation of breast cancer cells might be the result of delayed releasing of EPI.