The dry-wet cycle has a serious impact on the grotto sandstone, causing a large number of cantilever cracking damages to the grottoes. Through indoor dry-wet cycle test, Brazil split test and strain field analysis methods, the strength and mechanical parameters of the sample under different numbers of dry-wet cycles are analyzed and studied. The internal friction angle φ, cohesive force c, microstructure, strain field characteristics The law of change. The study found that with the increase of the number of dry-wet cycles, clay minerals gradually lost and the structure became loose. The weakening of the cementation between mineral particles led to the decrease of the cohesive force c of sandstone. At the same time, due to the change of the particle shape and pore structure of the sandstone, the contact relationship between the particles was changed, which led to the reduction of the internal friction angle φ, and finally caused the deterioration of its tensile and fracture mechanical properties. Finally, combining the failure process and crack distribution of the sample, two failure modes of the grotto sandstone under different dry-wet cycles are summarized.