Abstract: The failure mode of circular convex slopes is analyzed through three-dimensional numerical analysis, which indicates that this type of slope is prone to an axisymmetric failure and the results based on a non-axisymmetric failure mode will over-estimate the stability factor. Through this analysis, a question is put forward if it’s always reasonable when a general failure mode in the 3D slope stability analysis is applied. For the axisymmetric failure mode, an upper-bound solution for the case with (=0 is presented through the limit analysis, and a limit equilibrium method for general type of soil is also proposed. Compared with the results from the plane-strain analysis, the stability of circular convex slopes is notably different. If the relative radius becomes smaller or the soil is nearly purely cohesive, the difference will become larger. When the slope angle is small, a circular convex slope will be more stable than estimated from the plane-strain analysis, and it will be reversed when the slope angle is large enough, which corrects a misunderstanding that the circular slopes are always more unstable.