Abstract: In practice, slopes often have complex geometries. Therefore, the 3D finite element analysis with strength reduction method was used to study the safety factors and failure characteristics of double-sided slopes which have concave or convex structures with different gradient combinations under three boundary conditions, and the results are compared with those of flat slopes. It is shown that comparing with the flat slope, the safety factor of the convex vertical side slope is less than that of the flat slope. For other convex slopes, the safety factor under rough-rough boundary condition is increased by about 3%. However, for concave slopes, the safety factor is higher than that of the flat slope, and the safety factor of the curved surface slope with 1∶2 gradient under rough-rough boundary condition is the largest, and is higher than that of the flat slope by nearly 10%, and about twice as much as that of other structure of concave slopes with the same gradient. When the gradients of two sides are different, the slope will slip along the side with the large slope angle. When the gradients of two sides are equal, the slope failure area is affected by the boundary condition type. Under smooth-rough conditions, the sliding failure occurs on the constrained side, while under the other two boundary conditions, the failure area is symmetrical.