In order to explore the macroscopic and microscopic cross scale properties of granite with different water contents in deep areas, axial compression tests, scanning electron microscopy (SEM) tests, and X-ray diffraction (XRD) tests were conducted to analyze the relationship between multi-scale fracture and strength reduction damage. The results show that in the anhydrous state, the macroscopic failure is mainly shear failure and the fracture surface is smooth, while the macroscopic failure with an increase in water content is mainly tensile failure, and the crack path is parallel to the main stress direction and overall loose. The micro fracture under low water content condition is intergranular fracture, while the high water content condition is a composite failure of intergranular fracture and transgranular fracture. The attenuation rate of the peak strength and elastic modulus in the middle stage of water absorption is 6 times that in the early stage, reaching the maximum attenuation amplitude and showing a nonlinear exponential decrease. In the later stage of water absorption, the attenuation rate of the two indicators rebounds to the previous state. The deterioration coefficient decreases with the increase of water content. In the early stage of water absorption, water molecules play a role in lubricating the internal minerals of the rock, while in the later stage, water molecules undergo erosion and softening, leading to a significant reduction in strength.