A soil nailing technique was proposed as retaining system for slopes and cuts. In this Study, software SLOPE/W version 7.0 was used by applying soil nail to improve the slope stability. The parametric modeling was also done to determine the effects of inclination of soil nails. The results showed that the safety factor of slope increased after the application of the soil nails. Besides that, the results of the parametric modeling show the range of the soil nail's inclination depends on the steepness of a slope. In addition, the soil nailing would produce the maximum values of the FOS when an optimum inclination of nails is applied. A highway impact load was applied to show it's effect on optimum nails inclination.