Hexu expressway is located in Jianghuai area. The periodic rainfall in summer induced long-term alternative saturation-loss-resaturation processes of shallow-buried rock layer below Hexu expressway. In order to study the deterioration characteristics of mudstone and sandstone in Jianghuai area under water-rock interaction, the experimental study on anti-shear, anti-compressionand Scanning electron microscopywere conducted for the samples taken from in situ in order to reveal the corresponding relationship and their validation laws between rock porosity structure and rock strength softness from macroscopic and microscopic levels during different wetting and drying cycles. The results showed that, water-rock interaction had a significant impact on the anti-shear intensity and anti-compression intensity void parameter of mudstone and sandstone. Rock cohesion and internal friction angle decreased fast with the increase of wetting and drying cycle times. When the wetting and drying cycles reached a certain value, the anti-shear intensity and anti-compression intensity of two types of rocks tended to be stable. The pore number, total area, the diameter and area of maximum micro pore and surface porosity increased with the increase of wetting and drying cycles. Based on the experimental results, the rock deterioration mechanism has been discussed, which provided a basis for the study of rock deterioration characteristics and the stability of Hexu expressway.