Abstract: The effect of rare earth(RE) oxide on the non metallic inclusions in hardfacing metals of medium high carbon steel was investigated by means of optical and scanning electron microscopes.The results show that,by adding a certain amount of RE oxide in hardfacing metal,the number of the inclusions with large dimensions was reduced and its dimension's distribution is under 8μm,so that the inclusions can be refined.In addition,the morphology of the inclusion can be improved,so that the number of long inclusions with large shape coefficient can be decreased and that with shape coeffcient near 1 can be increased.The content of hardfacing metal can also be modified by adding RE oxide,in which the oxides with Al,Si,La and oxide-sulphide with Al,Si,La can be formed,and harmful MnS and the complex inclusions with Al,Mn,Ti can be decreased.