Abstract: Microstructures and mechanical properties of Ti-6Al-4V laser butt weld joints were investigated.The results reveal that the microstructure of laser welded joints consists of coarse columnar crystals.The martensite in columnar crystals crosses like basket shape.Microstructure of HAZ consists of α+β+α', and distributs non-uniformed, the closer to fusion zone the coarser grains and the more martensite.The suitable welding parameters for 0.8 mm thick Ti-6Al-4V alloy are 1 100-1 300 W and 1.5-3.0 m/min.The mechanical property of weld bead is good, all the tensile specimens fails at base metal away from weld bead, the pattern of fracture shows dimple fracture character.