In-situ synthesis of the system of TiB ceramic particle reinforced Co-base alloy composite coating has been produced on titanium alloy surface by CO₂ flow transverse laser to improve the comprehensive properties of the material. Analysis shows that β-Ti,γ-Co,TiB and TiB2 ceramic phase and CO₂Ti reinforcement phase lie in the coating. Studies of microstructure on the coating by scanning electronic microscope (SEM),electron probe microzone analysis (EPMA) show that in-situ synthesis of TiB2 and TiB major ceramic phases disperse homogeneously in the γ-Co based alloy. With the increase of the content of Ti and B in cladding zone the form of reinforcement phase varies with chemical composition of the coating,and the small dispersed sheet and massive structure transform into column crystal structure with regularly oriented and uniform distribution. The wear resistance of the coating was evaluated with wear test. The wear loss of the coating is approximately 1/10 of the substrate material. Wear resistance of the composite coating is significantly improved.