At present, the model of the forming mechanism of the wavy metal interface during explosive welding can only give a quantitative or qualitative description of some aspects of the forming process, rather than fully explaining all the phenomena involved. In the study of explosive welding of the titanium-steel transition layer, the wavy interface was observed by scanning electron microscopy. When the scanning electron microscope was enlarged to 2000 times, the wavy interface turned out to be titanium drops forming island shape bonding interface in the copper. When the relative displacement of the two plates is large, the crest part of the interfacial wave will be pulled off and the "island" will be formed. The theoretical analysis and experimental study of explosive welding show that the Richtmyer-Meshkov instability mechanism can better explain the formation process of the wavy interface in explosive welding. In the process of explosive welding, near the collision point, a thin layer of melting zone will appear at the welding interface, and the material near the interface is in a quasi-fluid state. When the high pressure elastic-plastic stress wave arrives, the interface disturbance will be caused, and the disturbance caused by the previous stress wave will further develop under the action of a series of subsequent stress waves, forming a typical Richtmyer-Meshkov interface instability. Therefore, Richtmyer-Meshkov instability and freezing are responsible for the formation of various types of wavy interfaces observed in explosive welding.