Abstract：Aiming at localization and deficiency of existed fuzzy classification methods for rock mass quality in underground structures，the nonlinear weighting operation of fuzzy matrix as well as the interval feature of the weight vector and membership of the factors for the rock mass classification are specially studied considering the properties of the fuzziness and grade of factors. Moreover，by using nonlinear fuzzy matrix composition operator and interval mathematical theory along with the analytical method of relative superiority of the interval number matrix，the interval nonlinear fuzzy judgment method for rock mass classification is established，which can reduce the judgment subjectivity and enhance the influences of the adverse factors on the judgment results. So the method makes the rock mass classification much more rational and easier to operate. The computation results of practical engineering and its comparison with those of other classification methods show that it is reliable and reasonable.
