Due to many uncertainties in the geotechnical mass

the appreciation of the slope stability is very difficult. On the basis of the conclusion that the uncertainty of the computation parameters is the main factor which influences the reliability of the stability analysis

the fuzzy set theory is used to consider the uncertainty of the computation parameters; and the constitution method of the fuzzy parameters and the idea for analyzing the uncertainty are put forward. By this way

the cut intervals of the safety factor under different membership degrees can be easily calculated according to the corresponding cut intervals of parameters; and the reliability index of the slope stability and the recommended single safety factor can be got. Different examples are studied; and it is shown that this method can fully consider the uncertainty of the computation parameters; and the obtained safety factor is more reasonable and reliable.