Abstract: This paper starts from plastic limit analysis and builds a reliability calculation model of limiting condition for slope on the basis of the upper bound theorem. As the limit state function of the slope was too complex to be solved by the common reliability method, the response surface method is introduced as the"bridge" between the limit state function and the reliability calculation. Sampling points are optimized using quadratic orthogonal principle. The quadratic response surface function is established, which considers the correlation between parameters. An upper bound solution of reliability is achieved directly using the J-C method. Influences of variability of parameter(s) on reliability of slope were discussed.