There are some inconsistency issues in the evaluation results obtained by different rock mass classification quality methods. According to the combination evaluation idea, several fundamental methods were introduced to build the model for the classification of rock mass quality. The Dempster-Shafer theory of evidence is a very rigorous uncertainty reasoning method with strong capability for information fusion and reflects the consistency and conflict of different information. This paper introduced the D-S theory of evidence to establish a new synthetic rule for the building of a new model of the combination evaluation. Then, due to the combination rule of D-S theory of evidence, which is difficult to define the basic probability assignment, Euclidean distance was introduced to build a method to define the basic probability assignment, and ultimately the combination evaluation method for the classification of rock mass quality based on D-S theory of evidence was established. Finally, a practical project shows that confliction exists in the three fundamental methods but D-S theory of evidence can solve this problem.