The metallurgical bonding and reliable joining of Mg/Ti dissimilar metals are restricted by their nonreactive and immiscible characteristics. To overcome this problem, laser lap joining of Mg/Ti with addition of Al interlayer is carried out. Well appearances are obtained by adjusting the welding parameters. Elemental distribution across the interface and bonding mechanism are studied. The results indicate that wettability of Mg/Ti is improved with the help of Al interlayer, and thus metallurgical bonding is accelerated. When the thickness of Al interlayer is 50 μm , the shear force reaches 1010N/cm, which is 1.8 times as much as that without Al interlayer. The interfacial microstructure indicates that AlTi3 phase forms at the direct laser irradiation zone, while α - Ti is at the zone around it at the interface. The second phases in the weld zone increase with the increase of thickness of Al interlayer. The tensile- shear force decreases when network structure is formed in the weld zone.