The ultrasonic welding technique can be carried out in many different ways, such as in direct welding metals both quickly and easily when compared to other welding methods. This paper gives a description of an experimental study of the ultrasonic welding of aluminum and cupper under water bath. For example, the ultrasonic welding of Al (t : 0.2) /Cu (0.2) can be accomplished when the conditions of welding pressure : 20MPa, at a required duration of 1.0s under water welding. Moreover, the material can be processed easily, and it gives out little heat, and hardly gets weakness.