The macroscopic mechanical behavior of red-bed soft rock under different drying-wetting cycles was analyzed by uniaxial/triaxial compression tests, and the evolution of mineral components was analyzed by x-ray diffraction. Considering the characteristics of porosity and mineral composition, PFC2D was used to establish the meso-particle calculation model for mechanical tests. The macro-meso cracking characteristics and mechanism of rock treated by dry-wet cycle were discussed. The results show that the content of quartz and clay minerals in rock increases under dry-wet cycle treatment. Cementation degradation between mineral particles and dissolution leads to micro-cracks between and within particles. Under compressive load, the essence of the change of the macroscopic failure mode is the change of the dominant type of the micro-crack.