With Al-Si welding wire ER4043, lap joint between aluminium and titanium alloy was made by MIG welding-brazing process with nocolok flux aiding filler metal in promoting metal wettability. A thin intermetallic compound layer was formed at the interface between the weld metal and titanium alloy and the layer mainly consits of TiAl3 phase. The tensile strength of the joint can reach 151MPa and fracture occurred in aluminium base metal.