The critical strength parameter pairs are calculated by reversely using the upper-bound limit analysis with polar slice method, which are treated as fitting data to obtain the seismic global limit response surface. The seismic global limit response surface is then regarded as kernel function and applied to Monte Carlo simulation to obtain the seismic failure probability and corresponding reliability index of reinforced slope with prestressed anchor cable, which avoided redundant and nested calculations by directly using the upper-bound limit analysis. In addition, this method is applied to a typical slope case which is reinforced with prestressed anchor cable. The results of limit response surface based on “the most adverse sliding surface with mean parameter” is calculated and compared with ones of global limit response surface. The results show that the failure probability of global limit response surface is larger than the other one; therefore, the method based on specific limit response surfaces may tend to be unsafe. Moreover, the influence of anchor parameters on seismic failure probability and the relationship curve between failure probability and reliability index are analyzed respectively. This method gives consideration to both the global variation of parameter space and efficiency of computation, so as to provide theory references for the seismic design of reinforced slope with prestressed anchor cable based on reliability index.