Concrete dam safety is one of the hot issues in dam study with the increasing of dam’s scale and height. Sliding failure along foundation surface is a potential failure mode of concrete gravity dam, and this mode is relatively rare in practical engineering. Strength reduction method is used to analyze the progressive failure along foundation surface of concrete gravity dam, and the strength parameters of weak layer in the foundation surface are reduced to analyze the occurrence and development regularity of plastic zone. If the plastic zone of foundation surface is totally coalescent, the dam will slide along the foundation surface. To track this process, the failure path and the safety reserve coefficient would be determined. This result will provide certain scientific basis for anti-sliding stability analysis of concrete gravity dam.