In the paper

based on the prognosis of space instabilities of slopes and their mapping inChongqing city by information method

the random searching for the location of sliding surfacesand their failure probability prediction are made by selecting typical seetions from the two kindsof instable slopes.At the same time

the failure probability values( FP_s ) for this two kinds ofslopes are gaven。 Here

the shearing strength coefficients c and tan are considered as the ran-dom variables.Finally

the FP values are combined with the colour map which is drawn auto-matically by computer to show the instability degrees of slopes in Chongqing city。