In the present work, titanium mono-boride (TiB) was dispersed in the weld metal of titanium through gas tungsten arc welding process in order to reinforce the mechanical properties of titanium weld. The microstructure difference of weld metal between the TiB-reinforced titanium and pure-titanium were made clear by the observation in the surface and cross section of weld metal, by using OM and SEM micrographs. The cell-network was formed in TiB-reinforced weld metal. The contrast of the cell-network was formed by the aggregate of TiB whisker crystals and the average grain size was refined in the case of TiB-reinforced weld metal. The distributions of TiB were analyzed in detail with transmission electron microscopy. It was found that the hardness increased in TiB-reinforced weld metal suggesting increasing of tensile strength. Furthermore, it was found that the bead width and the penetration depth were affected by the boron addition. In the case of TiB-reinforce weld metal, the bead width was wider and the penetration depth was shallower than those of pure-titanium. It suggested that surface tension distribution on the weld pool was changed due to boron segregation and the direction of convection flow was changed in Ti-B system.