The slope stability analysis with the shear strength reduction FEM can make the Rock and soil slopes achieve the limit failure state, and direct sliding surface location and slope stability safety factor can be obtained. From 3D perspective, through a variety examples of different loading conditions are calculated, the safety factor and the destruction mechanism of slope under the action of gravity and uniform rigid overload are researched and the results of two-dimensional limit equilibrium, 2D and 3D strength reduction FEM of calculation are compared. The results showed that Strength reduction FEM can be accurate and effective application of three-dimensional slope stability analysis. The results showed that: Strength reduction FEM can be accurate and effective application of three-dimensional slope stability analysis; Three-dimensional safety factor than plane strain conditions is to be larger, but little difference; With the load from the edge slope crest farther, the safety factor is greater. In addition, the location and size of slide of every cross sections of 3D slope is not same. Therefore, using simplified plane strain is too conservative, some important projects should complement the slope 3D finite element analysis.