In order to study road characteristics of high liquid limit soil of granite residual, the subgrade soil samples of an expressway in Hunan Province were taken for laboratory tests. Through XRF, XRD and thin section experiments, the mineral composition and basic structure of the soil samples were analyzed. It is found that the interaction between fine grained/flaky mica and fine grained clay contribute mostly to the specific properties of this soil. The effects of compaction energy and water content on the compaction index, compaction degree and CBR strength of the granite residual soil were studied and the change of state parameters of the soil samples which have been submerged in water for four days were analyzed. The results reveal that in order to get denser soil for the direct application to subgrade filling, the medium and low water contents have to be matched with large and small compaction energy respectively. The variation of peak values of CBR curve under different compaction energy is contrary to the compaction curve. Furthermore, the relationship between loss rate of CBR strength and water content before the submersion was established based on the comparison and analysis of the changes of its CBR strength before and after four day submersion in water. This study can provide some reference for the engineering application of high liquid limit granite residual soil.