Abstract: Based on the domestic and foreign research on retaining walls with shear key, the influence of shear key on improving sliding resistance stability of retaining walls is discussed. The mechanism of shear key and its design calculation methods at home and abroad are presented. There are large differences among different key design methods, most of the methods recommend setting shear key at the wall heel or middle of bottom plate. However, field observation found that the passive earth pressure in front of the key that is set at the middle of bottom plate under normal working loads is much less than the design expectation, while the effect of setting shear key at wall toe is verified by field observation and model tests. Based on the understanding that the anti-sliding force is only related to the shear strength of foundation soil, an anti-sliding stability formula for retaining wall with key at toe is deduced according to limit equilibrium method, and this formula is consistent with the anti-sliding stability formula of the bottom slab inclined to the filling direction proposed in Design Specification for Hydraulic Retaining Wall. For the retaining wall of revetment, the key located at wall toe can not only elevate the bottom plate and improve the foundation stress, but also alleviate base uplift pressure and improve the scour resistance, so it is widely used in the revetment engineering.