The pore water pressure is the essential factor and plays a key role in the unsaturated soil parameters. Experimental works and numerical analysis were conducted to determine the critical condition of the slope stability due to the evolution of shear strength parameters. The effect of infiltration on the pore water pressure was evaluated. The filter paper method was conducted to obtain the matric suction in various degrees of saturation. The mechanical properties of the undisturbed samples were examined through triaxial and permeability test, respectively. WRPLOT ViewTM was adopted to assess the intensity and duration of the actual rainfall. The applicability of the psycho-empirical method in SOILVISION Database to fit Soil Water Characteristic Curve (SWCC) was studied. GEO-SLOPE was used to assess the evolution of the pore water pressure and its effect on the safety factor of the slope. The evolution of pore water pressure induced the infiltration influenced the shear strength parameters and reduced the safety factor. The reduction 20% of cohesion was obtained and hence, the safety factor decrease to 1.0. The infiltration at the beginning of the wet season is the most critical condition that increases the soil moisture significantly.