Abstract：Aiming at the randomness and fuzziness for determining parameters of rock¢s shear strength，firstly，a method is put forward to express parameters of rock¢s shear strength using asymmetric triangular fuzzy numbers，which can reflect the interval features and probability distribution of parameters of rock¢s shear strength. Secondly，the sum of interval width of asymmetric triangular fuzzy numbers under some cut level together with square of the difference of weight between testing values and most probability calculation values is regarded as objective function for fuzzy optimistic analysis；and the determining method for the suitable cut level of asymmetric triangular fuzzy number is proposed by using “3s” rule. Then，the approach to determine the reasonable cut level of asymmetric triangular number is developed；accordingly，a new method to determine parameters of rock¢s shear strength based on asymmetric triangular fuzzy numbers is established. This method can reduce the effect of abnormal testing data on the most probability analysis results and can reflect the uncertainty features for determining the parameters of rock¢s shear strength. It can provide a new method for deciding values of mechanical parameters for the uncertainty analysis of rock engineering. Finally，the analysis of practical engineering computation and relative comparison to other methods shows that the proposed method is reasonable.
