Abstract: In order to improve the deformation coordination between core wall and bank slope, the high core rockfill dam is usually equipped with high plastic clay between the core wall and the bank slope, which is collectively referred to as the contact clay. The deformation characteristics of the 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 the clay and the bank slope, and the shear displacement of interface at different elevations of prototype dam is discussed. Based on theoretical analysis, an analytical expression is proposed to calculate the boundary effects in the centrifugal model tests on the interface between the clay and the 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 the contact clay and gravel core-wall soil is mainly vertical settlement, and the settlement contour between the contact clay and the 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 effects between the contact clay and the bank slope should be considered in the structural safety analysis of high core rockfill dams.