Abstract: Cantilever retaining wall supported by earth berm has been widely used in excavation. However, the design method is absent in the specification, and the analysis method for earth berm support often involves specifying a slip surface artificially or using a cumbersome calculation process. Therefore, the soil pressure distribution on both sides of the cantilever retaining wall under undrained conditions is determined using the Coulomb sliding wedge analysis and strength reduction method. The embedded stability safety factor is then derived from the soil pressure distribution. The sliding wedge analysis results show that the slip surface on the excavation side during earth berm support does not follow the traditional Rankine passive slip surface. Instead, it is divided into three sections from top to bottom, passing through the earth berm slope, the right end of the earth berm and the horizontal excavation surface. This proposed method considers the shear force between soil and wall, and the calculation results agree well with the finite element analysis. Based on this method, the influences of the earth berm size and the embedded ratio of the retaining wall on the safety factor are studied.