In this paper, in-situ synthesized titanium matrix composites (TMCs) reinforced with TiB whisker plus La₂O₃ particle were successfully fabricated by the laser beam welding (LBW) process with a Nd:YAG laser source. The evolution behavior of TiB was investigated during laser welding. Optical microscope (OM), X-ray diffractometry (XRD) analysis, scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) were used to analyze the phase, distribution and morphology characteristics of TiB whisker reinforcements in the laser weld seam, and the interface between TiB whiskers (or La₂O₃ particles) and titanium matrix was also discussed. Research results show that TiB is still retained in the welding joints, and no harmful substances are found. TiB is significantly refined and redistributed at b grain boundaries, a novel network structure forms in the fusion zone and the heat-affected zone near the fusion zone. Relatively, only some TiB whiskers in the heat-affected zone far away from the fusion zone change their sizes through intensi?ed diffusion of boron, and TiB near the base metal exhibits no changes and similar morphological features with that in the base metal. Further examination by TEM proves that interfaces between the reinforcements and the titanium matrix are very clean, and TiB maintains good bonding relationship with the matrix. There is no interfacial reaction which explains that interfacial microstructures between the reinforcements and the matrix are very stable during welding.