Abstract: Stepped amplitude and constant amplitude were adopted in ultrasonic welding of dissimilar thin metals,aluminum plate and nickel plated steel of lithium battery electrode tab in 0.1 mm thickness.The surface morphology of welded joint were observed by 3D confocal laser scanning microscope,and the strength of welded joint was measured by peeling test,and then its standard deviation was calculated.The results show that the welded joint using stepped amplitude had a higher strength and a stable standard deviation of strength,adhesion between tool head and joint surface reduced,the surface was smooth after peel test,and serious cracks of the relatively soft metal during the process of welding reduced when compared to using constant amplitude.