Slope stability of unsaturated slopes during rainfall is one of thea serious geoenvironmental disastersgeo-environmental disaster. Many natural slopes werehave been subjected to change in geometry to allow for the construction of infrastructure. This paper presents stability analysis of a natural unsaturated slope, subjected to cutting, to make room for the development of irrigation canals in the Khodafarin project. Physical and mechanical properties of the soil samples were examined in the field and laboratory. TriaxialTri-axial and permeability tests were conducted to analyze the shear strength parameters and coefficient of permeability on the saturation conditions, respectively. Rainfall events with 50 yeara 50-year return period were adopted to assess the intensity and duration of the actual rainfall. The RETC code is adopted for quantifying the hydraulic functions of unsaturated soils to fit the Soil Water Characteristic Curvesoil water characteristic curve (SWCC). The finite difference analysis of transient water flow through unsaturated–saturated soil is carried out to study the effects of rainfall infiltration on pore pressure generation, degree of saturation, slope stability, and shear strain increment during rainfall e. The FOS values are evaluated using the shear strength reduction technique.