Abstract: Interfacial reaction of immiscible and nonreactive Mg/Ti dissimilar joint was improved by Al element from AZ91 Mg based filler (9 wt.%), coupled with laser local heating characteristics of laser welding-brazing method. The effect of the process parameters on weld quality was investigated. Microstructure and mechanical properties was then analyzed. The results indicated that reliable joining was achieved between Mg alloy and Ti alloy using AZ91 filler. The maximum tensile-shear force could reach 1 520 N. Segregation of Al element at the interface from filler was observed after laser fast heating and cooling, and reacted with Ti resulting in newly formed compound AlTi3. The thickness of reaction layer was ultra-thin at approximately 2 μm. Above all, metallurgical bonding was realized while the thickness of reaction layer was kept below a certain value which did not affect the mechanical properties.