The ultrafine electrolytic copper powders were coated by silver using a combination of displacement reaction and reduction method, and the bimetallic core-shell powders with a 10wt.% addition of silver were obtained. The effects of concentration of complexing-dispersing agent and reducing agent on the silver coating layer were studied. The morphology, composition and structure of bimetallic core-shell powders were characterized by scanning electron microscopy, X-ray diffraction and energy dispersive spectroscopy. The oxidation resistance and electric conductivity of the coated powders were also investigated. The experimental results showed that the powders have a better oxidation resistance and higher conductivity using the complexing-dispersing agent of 10g/L EDTA-2Na and the reducing agent n of 30 g/L formaldehyde.