Abstract: To investigate the growth inhibition effect of a copolymer composed of artesunate ( ART ) and magnetic nanoparticles of Fe3O4 ( MNPs-Fe3O4 ) on K562 cells and explore its potential mechanisms. Methods: The protein expression levels of Bcl-2, Bax, Bcl-rambo, Caspase-3, and Survivin in K562 cells treated with or without the copolymer of ART with MNPs-Fe3O4 were measured by Western blot. The cytotoxicity of the copolymer on K562 cells was determined by an MTT assay. The copolymer-induced apoptosis rate of K562 cells was measured by flow cytometry. Results: ART could inhibit the proliferation of K562 cells. When treated with the copolymer of ART with MNPs-Fe3O4, the K562 cell proliferation inhibition rate was significantly increased compared with that of K562 cells treated with ART alone ( P < 0.05 ). Flow cytometry results demonstrated that the apoptosis rate induced by the copolymer more significantly increased than that by ART alone ( P < 0.05 ). These results suggest that MNPs-Fe3O4 can enhance the activity of ART. Interestingly, copolymer-induced cell death was attenuated by the caspase inhibitor Z-VAD-FMK. The results also indicate that when compared with ART alone, the copolymer of MNPs-Fe3O4 and ART up-regulates the expression of Bcl-2, Bax, Bcl-rambo, and Caspase-3 proteins in K562 cells, but down-regulates the expression of Survivin protein. Conclusion: The results suggest that MNPs-Fe3O4 synergistically increases the apoptosis induced by ART in K562 cells, which may be related to the up-regulation of Bcl-rambo and down-regulation of Survivin.