Slope stability analysis remains an active and important area of study for geotechnical engineers. The vast majority of slope stability analysis is performed in two dimensions. But in real practices, 3D slope results are more reasonable. Due to the remarkable increase in computational power and falling costs in recent years, meaningful 3D analysis can now be performed on a conventional desktop or laptop computer. In the present paper, a two-dimensional limit equilibrium model was established by LiZheng Slope Analysis Software. Using the FLAC3D program, a 3D plane strain model was proposed and the stability analysis was implemented, placing the results in context with 2D methods. The results show that safety factors got from the 3D plane strain model were closest to the Simplified Bishop method, and the average deviation of these two methods is 1.6%, the largest deviation is 3.2%. With the refinement of FE mesh or improvement of element type, the deviation could be smaller.