Abstract: The ultrasonic friction welding (UFW) method was employed to realize the joining of 20-25 μm thick Al-Al foils without the introduction of difference to parents materials, since the conventional UFW puts more focus on large scale of bulk metal materials. The monomer and post-joining Al foils were analyzed and compared including surface roughness, thickness uniformity, and interface characteristics by using white light interfere profiler (WLI), optical microscope (OM) and scanning electron microscope (SEM). The experimental results indicate that the high quality Al-Al foils components and one kind of Al-Al device are well prepared by our improved UFW.