Purpose: The purpose of this study was to investigate to effect of the electro-polishing condition according to electrolyte temperature and current and polishing time on surface morphology and composition by scanning electron microscopy(SEM) and energy dispersive X-ray spectrometer(EDS) in dental casting Co-Cr-Mo alloys. Methods: 16 specimens were divided into 4 groups which have each 4 specimens. The size of specimens were 10mm wide and 5mm height. the electro-polishing of specimens are by polishing solution temperature and times in Co-Cr-Mo alloy by SEM and EDS analysis. Results: The results shows that most smooth surface is obtained when electro-polishing is performed at $49^{circ}C$ for 30-40sec with electro gap of 10mm and 8 voltage. Conclusion: The morphologies of specimens after electro-polishing were scratch absent and significant between at $40^{circ}C$ for 45sec and at $49^{circ}C$ for 45sec.