Abstract: The microstructure in various zones of laser welded joint of BT20 titanium alloy with 2.5 mm thickness was observed and the mechanical properties,such as the microhardness,the tensile and the bending properties,the fatigue life and the fracture toughness of the joint at room temperature,were tested.The microstructure in various zones consists of martensite and the microhardness of the joint is higher than that of the base metal.The tensile strength of the joint is equal to that of the base metal and the ductility of the joint is slightly lower.The stress level has an important influence on the fatigue life of the joint,which is equal to that of the base metal at low stress level but obviously lower at high stress level.The fracture toughness of the weld metal is lower than that of the base metal and the fracture toughness of heat-affected zone(HAZ) is intervenient between those of weld metal and base metal.