<p>Rainfall increases the moisture content of rocks, alters their internal structure, and weakens their mechanical strength, thereby compromising slope stability. Therefore, exploring the potential impact of rainfall on rock slopes is crucial. In the paper, the compressive strength of rock in dry and wet environments was studied by dry-wet cycle test. The regression analysis method was used to explore the internal relationship between uniaxial compressive strength and dry-wet cycle times of tuff under different sizes. The results show that with the increase of the number of dry-wet cycles, the uniaxial compressive strength of the rock decreases gradually and decreases exponentially. The total water absorption rate increased with the increase of the number of cycles, but the increase rate gradually slowed down. The number of dry-wet cycles significantly affects the fluctuation coefficient of uniaxial compressive strength, but this effect gradually weakens with the increase of size. The normalized curve of uniaxial compressive strength shows a downward trend with the increase of dry-wet cycles, indicating that the rock has obvious deterioration. There are differences in the degradation rate and degree between rocks of different sizes. This study proposes a quantitative model for the combined effect of wet-dry cycle times and rock size on compressive strength and reveals the regulatory mechanism of size on rock degradation process through normalization and fluctuation coefficient analysis. The research results provide theoretical and parameter support for predicting the stability of rock engineering under wet dry environment coupling conditions.</p>