TiNi memory alloy and TC4 titanium alloy dissimilar materials were welded by ultrasonic welding with nickel and pure aluminum as transition interlayer materials. The effects of different process parameters on the morphology and mechanical properties of TiNi/TC4 dissimilar metal welding joints were studied. The results show that the plastic deformation of materials near the interface of Al interlayer is much larger than that of Ni interlayer, and a large amount of Al is extruded from the interface. Welding time and pressure have a significant effect on the tensile shear force of welded joints, and the tensile shear increases first and then decreases with the increase of welding time and pressure. The ultrasonic welding process will also change the microhardness of the weld zone material, parallel to the direction of the bonding surface, the core position compared with the unwelded base material hardness has a small increase, perpendicular to the bonding surface direction, the closer to the bonding interface, the higher the hardness of the material, but the increase of the two generally not more than 10%.