Abstract: There are several discontinuous planes dipping upstream in the abutment rock mass of an arch dam. Through the geome-chanics model tests No.1, No.2, No.3 and No.4, the upward sliding phenomenon of the abutment of the arch dam in model has been found from both positive and negative aspects. As the structure measures of the resistance and control over the upward raise are tak-en gradually from test No.1 to No.4, the degree of overload safety of the dam enhances from less than1.5～1.7 P0 to 3.5～5.4 P0 or 3.5～4.5 P0 which is acceptable. The main cause is that the inverse sliding of the rock mass of the upper plate occurs. Being different from the upward sliding along the foundation contact surface, it develops along the discontinuous plane dipping upstream in the rock mass.?