Solid powder boriding experiment was carried out on TC4 titanium alloy surface with method of RE(rare earth)-boriding at the temperature of over 1000°C. By means of XRD, SEM and EDS, phase composition, microstructure and morphology of TC4 titanium alloy after RE-boriding were investigated. The effect of rare earth on phase composition was discussed. Results of the experiment showed that the diffusion layer was composed of top-layer TiB2 and sub-layer TiB whiskers with the highest thickness being 25μm. The XRD results revealed TiB-TiB2 biphasic B-Ti compounds layer formed on the surface of TC4 after RE-boriding. The high content of B and Ce in the surface layer showed rare earth increased the absorption and concentration of B atoms.