Sichuan—Chongqing area contains a significant number of grotto sites, representing a pinnacle of late- stage grotto development in China. The grotto rocks primarily consist of late Mesozoic continental red- bed sandstone from the Sichuan Basin, characterized by a loose pore structure. These rocks have been subjected to long- term exposure to regional hot—humid climates, heavy rainfall, and human activities, resulting in widespread and complex weathering damage that endangers the safety and longevity of the grotto relics. This paper provides a comprehensive review of previous studies to explore the impact of the physicochemical properties (e.g., pore structure, mineralogy, and chemical composition) of the fresh grottoes sandstone in Sichuan—Chongqing area on its mechanical behavior. It elucidates the main changes in mineral and chemical composition before and after weathering, as well as the general trends in the content of major oxides (SiO2, Al2O3, CaO, MgO, Na2O, K2O, etc.) with sampling depth. Analysis of climate—weathering coupling indicates that these grottoes experience a moderate chemical weathering regime, promoting secondary clay formation and salt damage (e.g., Na2SO4·10H2O). Furthermore, the silica- to- alumina ratio (R) and Ba2 chemical weathering indices effectively correlate with the uniaxial compressive strength of fresh sandstone, with their normalized values providing a good indication of weathering degree. During temperature and humidity cycles, the repeated water-induced swelling of clay minerals and the crystallization—dehydration cycles of soluble salts such as mirabilite are two key factors associated with the damage of the sandstone surface structure. Additionally, mineral morphology, rainfall intensity, surrounding rock pressure, and sedimentary environment also exert complex and far- reaching impacts on the weathering of sandstone grottoes in this area.