The laser welding processing of 10mm thickness TA5 titanium alloy by using10KW high power fiber laser was syudied. The high speed photography shows that when the laser power reaches 3~4KW, the plume become serious, and the splash and soot increase obviously. The weld metallography test shows that the weld section is "wedge-shaped" when the laser power is low, while the weld section becomes "funnel shaped" when the laser power is more than 6KW.When the laser power is set 10KW~11KW ,and the welding speed is 1100~1500mm/min，an excellent "Key-holding" welding joint is obtained，and the welding seam become typical high-energy beam joint shape with a big ratio of depth to width is up to 2:1. RT and PT test of the weld seam show that NDT standard can be met.The mechanical test shows that the strength of the welded joints can reach 800Mpa, and the bending standard can be met，The fracture dimple is obvious, which indicates a ductile fracture. Metallographic test shows that the section of weld zone is "girdle-shape" morphology and the columnar crystal zones are obvious, with each columnar crystal zone showing obvious competitive growth mode. The weld zone is mainly serrated α+punctate β. The hardness test shows that the hardness of the weld zone is slightly higher than that of base metal, and the hardness of heat-affected zone is the lowest, which meets the hardness requirements of titanium alloy joint.