Abstract: Because the uncertainty of physicomechanical paramenters is characteriste of rocks, based on the concept of the fuzzy mathematics) a new method to classification of the rock engineering are proposed. First the rock are divided into κ kinds, e. g., the excellent one, the very good one, etc. Each kind corresponds to a fuzzy set λ_i, i = 1,2,……k, respectively. For the rock used in a practical engineering, the n aspects of the com-pressive strength, ground water, ete as a single factor are evaluated. After transferring them into fraction unitedly, n fuzzy sets are found. Then we set m series of the weighted numbers and explains the various probabilities of the proportion of different factors in the comprehensive evaluation. Finally we can obtain a comprehensive evaluation for each series of the weighted numbers and engineering classification of rocks.