Slope stability and reinforcement measures of an earth-rock cofferdam on deep overburden foundation are studied in the paper. Slope stability is analysed by using FEM strength reduction method, considering seepage, based on ABAQUS. Two different reinforcement measures are taken: vibro-replacement stone columns and concrete anti-sliding piles. As a result of the research, conclusions are made: overflow happens on the slope near bottom of the foundation pit in layer Qal-1, where permeability coefficient is quite large compared to that of other layers; Both the vibro-replacement stone columns and concrete anti-sliding piles increase the stability; Vibro-replacement stone columns should be used as the final reinforcement measure, since vibro-replacement stone columns can be constructed before the foundation pit excavation and they can also conduce to drainage in foundation pit. This deep overburden foundation is characterized by complex geological conditions and poor mechanical properties. Therefore, the successful construction of the project has a certain reference and application value.