Abstract: Slope instability is related tothe relaxation region caused byslope cutting. It is very importantto properly determine the relaxation region when a cutting slope is remedied. From the theoretical results of stress analyses for a cutting slope, it is pointed out that the stress and displacement of the slope become smaller and smaller away from the slope surface. The concept of relaxation region is given. It can be determined based on the stress or displacement curves for different reference lines horizontal or parallel with the ground line on the slope top. In addition, the numerical analysis flow chart is given, and by taking a practical project as an example, the way to determine the relaxation region is explained.