In this thesis, two cases of slope failure have been extensively examined in order to establish typical reinforcement methods for similar situations to these cases. In the case of the field example(A), an arc rotational and wedge-shaped slope failure has been caused by the boundary face of the weathered rock floor, resulting from heavy rainfall. In order to ensure the slope stability, the angle of slope has to be lowered by removing the loosened soil, and a combination of the stair type retaining wall and permanent anchor method can be implemented. In the case of the field example(B), it is not the failure of the arc which can be generated in the fracture zone or soil, but the combination of a wedge failure by the joint intersection and a plane failure. As the frictional force in the joint face is smaller than the energy slidden by block weight, the failure is considered to be a block type failure. A number of more cases of slope failure should be compiled, summarized, and thoroughly examined to give some guidances for securing slope stability.