The improved slope mass rating method(SMR) is proposed

through integrating the gray system theory with traditional SMR method. The quantitative indexes value of traditional rock mass classification methods was very discrete

resulting in the step change in classification. The problems of small samples and discrete issues are solved by using features of gray system theory. Firstly

the evaluation indexes of traditional rock mass quality classification are classified. Also

the weights of indexes are determined; and the triangle whiten function for evaluation indexes is built. Furthermore

the rock mass quality classification of slopes is valued based on the maximum degree. Finally

combining with a slope case study and comparing general engineering rock mass classification methods(RMR and SMR)

the result judged by improved SMR method can agree well with engineering facts; and it expresses a high and strong quality grade stability. For rock mass quality classification in slope engineering

this study shows that this method is scientific and accurate.