Traditional reliability analysis of slope is often performed under linear Mohr-Coulomb (M-C) failure criterion assumption and using limit equilibrium method or finite element method which is for calculating the safety factor. However, the failure criterion of geomaterials is nonlinear. In this paper, upper bound reliability analysis of slope is performed using upper bound limit analysis and Monte Carlo simulation based on nonlinear Mohr-Coulomb failure criterion, which is for a more practical description of the failure mechansim of geomaterials and obtaining strictly accurate answers. When the nonlinear parameter m is equal to one, the expressions in this study convert into linear Mohr-Coulomb failure criterion, and thus the feasibility of this study is verified by comparing with other results. Meanwhile, initial cohesion, internal friction angle arctan(c₀/σ_t) and nonlinear parameter are selected as the stochastic parameters which are considered to have a truncated normal distribution, and the effects of variability and sensitivity of parameters are analysed. The results show that reliability of slope decreases with the variability of initial cohesion, internal friction angle arctan(c₀/σ_t) and nonlinear parameter; reliability of slope increases with initial cohesion and internal friction angle arctan(c₀/σ_t), and decreases with nonlinear parameter.