Fuzzy evaluation systems have been widely applied to comprehensively evaluate the slope stability. When material parameters of rock masses are used as evaluation factors, due to their discreteness in practical engineering, these parameters are required to be evaluated in advance to obtain characterization parameters. Then the characterization parameters are employed in comprehensive evaluation. From the viewpoint of rock masses resisting on external interactions, the characteristics of rock masses of Dagangshan abutment slope are studied in depth by considering the range and sequence of deformation and the safety factor before and after slope failure. Specifically, these characterization parameters are obtained by analyzing layered sensitivity and evaluating each parameter and the membership degree is derived by the area distribution method. Besides, the comprehensive sensitivity of mechanical parameters of rock masses is investigated by referring safety factor and the displacement. The weight of each factor is further determined by its sensitivity, and then applied in the comprehensive evaluation system. It is found that the deformation of rock masses mainly depends on cohesion when the displacement is regarded as reference. The frictional angle has more effect on slope failure than the cohesion when the safety factor is regarded as reference. The results also indicate that the sensitivity characteristics of displacement are better than those of safety factor. The results of comprehensive estimation reveal that rock masses have a group of intensive mechanical parameters. It is also noticed that evaluation results are better when the safety factor is used as reference, which is in accordance with the results of sensitivity analysis and practical circumstance, and thus the reasonability of the proposed method is verified.