Abstract: It is indicated by the investigation of comparison between addition and non-addition of rareearth elements that transverse breaking strength was obviously improved after appropriate additions of rare-earth in cemented carbide. X-ary quantitative analysis shows the additions of rare-earth can control to greater extent the martensitic phase change of cobalt phase in alloy, remaining more α-Co with face-centered cubic structure. The investigation pointed out that this was the cause of cemented carbide strengthened by rare-earth.