In order to improve the deformation coordination between core wall and bank slope, high core rockfill dam is usually equipped with high plastic clay between the core wall and bank slope, which is collectively referred to as contact clay. The deformation characteristics of contact clay have a great influence on the stress deformation characteristics of high core wall. Four groups of centrifugal model tests are carried out on the interface between clay and bank slope, and the shear displacement of interface at different elevations of prototype dam was discussed. Based on theoretical analysis, an analytical expression is presented to calculate the boundary effect in centrifugal model tests of interface between clay and bank slope, so as to determine the similar scale of test model. The results show that at different elevations of the prototype dam, the interface between the contact clay and the bank slope will generate shear displacement. The deformation of contact clay and gravel core-wall soil is mainly vertical settlement, and the settlement contour between contact clay and gravel core-wall soil changes continuously without steep change, which indicates that the contact clay plays a good role in coordinating deformation. Therefore, the contact effect between contact clay and bank slope should be considered in the structural safety analysis of high core rockfill dam.