Determination of stable slope is one of the primary stages in open pit mine design. Chador-Malu iron mine is located in the North-East of Yazd province and reserve of this deposit is about 400 million tons. At pit walls of this mine observed instability. In this paper, the stable slope of pit walls is determined by using CLARA software. At first, based on geological section that provided by Russian experts, litological map of mine prepared and different zones at pit walls recognized. The existing rocks in the pit layout were divided into six geological zones and the Mining Rock Mass Rating (MRMR) was determined for each zone. Then, by using Hock-Brown criterion, the quantities of cohesion (c) and friction angle (f) were calculated fore different zones. Uniaxial compressive strength and density for different rock were obtained based on laboratory tests. Two different methods were finally used to calculate the stable slopes. In first method, stable slopes were determined for each zone in different heights from 15 to 225m. The safety factor values were plotted against slope angle in different heights of slope for each zone. Furthermore, the stable angle was determined for each zone on the geotechnical map. In second method, a trial-and-error approach was used to determine the stable slopes of each section.