The methods used to analyze the slope stability are commonly based on limit equilibrium theory and are expressed in terms of a factor of safety. However, an analysis that approaches the variability of the soil parameters and model uncertainties becomes necessary. In this paper, a pre-designed reinforcement slope available on the technical literature was chosen to a probabilistic analysis. The statistic information about the parameters was found in the literature and the numerical simulations were done in the software SLOPE/W. Besides, a parametric analysis was done varying the coefficient of variability of unit weight and friction angle to investigate the effect of the variability on the reliability of the slope. Also, the contribution of water level was measured. The results show relevant variation on the reliability index with the parametric analysis, indicating the importance of this study. Furthermore, the water level has a decisive impact on safety and reliability of the slope. Lastly, the reinforcement with geotextiles was efficient to increase the safety of slopes.