Weathered rocks can cause particular difficulties at every stage of project from investigation through the final execution and maintenance of the works. The selection of suitable design parameter, the adoption of proper analytical approaches, and the use of appropriate methods of construction may all be especially troublesome for engineering projects involving weathered rocks. These problems can be solved with an assistance of weathering degree classification of weathered rocks. However current approaches for determination of degree of weathering encounter many difficulties to use in practical as an effective method. A new attempt is proposed to define a classification of degree of weathering with reliability and less time-consuming in this study. Experimental program is established to evaluate chemical composition and water absorption ratio of samples for a classification of weathering degree. The use of chemical index of weathering and water absorption ratio are revealed as useful tools to clarify the weathering degree of weathered granite. Then, the degree of weathering is correlated with electrical resistivity properties at various degree of saturation. The relationship between degree of weathering and resistivity emphasize the applicability of electrical resistivity to clarify the degree of weathering of sample. Electrical resistivity properties of weathered rocks show a clearly decreasing tendency with the increasing of chemical index of weathering, water absorption at different degree of saturation. The electrical resistivity values may represent both physical and chemical characteristics of the material when the degree of saturation is considered. This study suggests that a method using electrical resistivity is an effective tool to classify the degree of weathering of a weathered rock.