Laser welding is applied to join 2.5mm thick dissimilar metals of Ti-22Al-27Nb alloy and TC4 alloy. The microstructure characterization and the mechanical properties of the laser welded joints are inves-tigated. The results show that a well-quality joint without crack or porosity can be obtained using laser welding method. The O phase and α2 phase gradually transforms to B2 phase in heat affected zone (HAZ) of Ti-22Al-27Nb alloy. The heat affected zone of TC4 alloy mainly consists of martensitic α′ and primary α phase. The weld metal is mainly composed of B2 phase and martensitic α′ phase. The average tensile strength of the laser welded joints is 1043 MPa, which is comparable to Ti-22Al-27Nb parent metal. The average elongation tested to be 5.65% is 49% of the Ti-22Al-27Nb parent metal. The tensile fractures are all located in the weld metal and the fracture surfaces are characterized by a ductile dimple feature.%研究激光焊接对2.5mm厚Ti-22Al-27Nb/TC4异种合金焊接接头组织和力学性能的影响。结果表明，激光焊接可得到表面成型良好、内部无气孔裂纹的接头。Ti-22Al-27Nb侧热影响区O相和α2相逐渐转变为B2相。TC4侧热影响区由α′马氏体和初始α相构成。焊缝区由B2相和α′马氏体构成。Ti-22Al-27Nb/TC4异种合金激光焊接接头平均拉伸强度为1043MPa，接近Ti-22Al-27Nb母材的强度。焊接接头平均延伸率为5.65％，为Ti-22Al-27Nb母材的49％。拉伸断裂位置均位于焊缝区域，断口形貌为韧窝花样。
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