Biocompatible and biodegradable magnesium(Mg)based metals have attracted great interest for use in orthopedic implants and devices.Based on our previous study that Mg with and without micro-arc oxidation(MAO)coating showed obvious cytotoxic effect on tumor cells due to the increase of pH value during the degradation of Mg,this study further evaluated the cytotoxic effect of Mg and MAO coated Mg on osteosarcoma(MG-63)cells by analyzing the cell adhesion,morphology and number through observation of scanning electron microscope,as well as live/dead staining,lactate dehydrogenase(LDH)activity and 4,6-diamidino-2-phenylindole(DAPI)assay.The results indicated that,compared to titanium,Mg could strongly inhibit the cell adherence,morphology and number of MG-63 on the surface of the naked Mg,whereas the MAO coated Mg showed relative weak cytotoxic effect on MG-63 cells,expecting that magnesium based metals with suitable coating can be designed to be applied as tumor prosthesis in the clinical practice. Biocompatible and biodegradable magnesium (Mg) based metals have attracted great interest for use in orthopedic implants and devices. Based on our previous study that Mg with and without micro-arc oxidation (MAO) coating showed obvious cytotoxic effect on tumor cells due to the increase of pH value during the degradation of Mg, this study further evaluated the cytotoxic effect of Mg and MAO coated Mg on osteosarcoma (MG-63) cells by analyzing the cell adhesion, morphology and number through observation of scanning electron microscope, as well as live / dead staining, lactate dehydrogenase (LDH) activity and 4,6-diamidino-2-phenylindole (DAPI) assay.The results indicated that, compared to titanium, Mg could strongly inhibit the cell adherence, morphology and number of MG- 63 on the surface of the naked Mg, whereas the MAO coated Mg showed relative weak cytotoxic effect on MG-63 cells, expecting that magnesium based metals with suitable coating can be designed to be applied as tumor prosthesis in the clinical practice.