<p>To examine the deformation, failure modes, and deterioration properties of sandstone containing water when exposed to acidic conditions, we initially performed uniaxial compression tests on sandstone specimens with varying pH levels and moisture contents. Microscopic fracture images were then captured using an scanning electron microscope. A quantitative assessment was conducted to analyze the reduction in strength, macroscopic and microscopic deformation, and failure characteristics, energy transformation, and the progression of damage in sandstone containing water. Finally, the damage degradation mechanism under acidic conditions was explored from a water-rock interaction perspective. The results showed that peak strength was lower in wet sandstone, with gradual reductions in elastic modulus (<i>E</i>) and compressive strength (<i>σ</i>) as water content increased. At 2.58% water content, maximum reductions in <i>E</i> and <i>σ</i> reached 42.3% and 43.07%, respectively. Failure initiated with microcracks, which expanded into through-going fractures and large spalling areas. Higher water content intensified the damage. Acid corrosion roughened fracture surfaces and increased porosity, with the most severe internal corrosion occurring at pH 4. Energy evolution during loading reflected microcrack compaction, initiation, propagation, and macroscopic failure. Increased water content correlated positively with damage, though high H⁺ concentration initially had a limited impact. This study can provide strong support for geotechnical engineering and environmental remediation.</p>