Abstract: Experimental study, on the interfacial perturbation originated from the complex structure of shock waves and the developments of Richtmyer-Meshkov instability by reshock, is presented. The motionless and stable N₂/SF₆ interface is formed in a vertical shock tube. The planar shock wave diffracted over a rigid cylinder, interaction with the flat interface, so the interfacial perturbation originated from the complex shock wave is studied. The interaction fields of shock waves with cylinder are complex, including the primary incident shock, triple point, reflected bow shock, Mach shock, slip lines originated from the triple Mach shock. The understanding of interaction of complex shock wave with planar interface, will contribute to the knowledge of the perturbation originated from the complex flow. After diffracted shock wave had transmitted at interface, the interface is divided into ″inner interface″ and ″outer interface″ by the first and the second slip lines. Experimental result shows a clear correlation between the form of interfacial perturbation and distance, which is between the point of intersection of the slip lines and the interface. Good agreement is found between the interfacial perturbation measurements with reshock and the Jacobs-Sheeley vortex model..