Abstract: Laser welding of TA15 and 5A06 alloys with 3 mm in thickness was conducted by focusing laser beam on titanium side,and the aluminum was melted through the heat conduction from titanium side. The effect of laser offset distance on microstructure and mechanical properties of the dissimilar butt joint was investigated. When the laser offset is 0.1-0.4 mm,fusion welded joint is formed. When the laser offset is 0.5 mm,fusion welded joint is formed on the upper side of the joint accompanying with Ti-Al intermetallic compounds. Welded-brazed joint is formed on the middle and bottom side of the joint accompanying with continuous Ti-Al intermetallic compounds layer with 1 μm thickness. The tensile strength of joints firstly increased and then decreased with the laser offset increasing. The highest average tensile strength of the joint reaches 181 MPa when the laser offset distance is 0.5 mm. The joints partly fracture in Ti-Al intermetallic compounds at the interface,and partly fracture at the fusion zone of aluminum alloy.