In-situ synthesized TiB system ceramic particle reinforced Co-based composite coating was prepared on titanium alloy surface by transverse flow CO2 laser to improve the surface service performance of materials. The composite coating was studied by XRD, SEM and EPMA. Results show that in-situ synthesized TiB2 and TiB major ceramic phases are dispersed homogeneously in the γ-Co based alloy coating; they are very thin and uniform; there is obvious difference between the dendrites and the intergranular on the microstructure and composition. The microhardness of the coating is increased prominently, whose average value is about three times higher than that of the titanium alloy substrate. Wear resistance of the composite coating is significant improved