Many precious cave murals around the world face challenges in preventive conservation. Opening these caves to the public alters their microenvironment, posing new challenges for mural conservation. While previous research has focused on specific climate impacts, the effects of public access across different climates remain underexplored. This study evaluates the impact of open caves on mural preservation in humid, semi-humid, semi-arid, and arid regions of China. Using a validated two-dimensional heat and moisture transfer model, this study simulates the hygrothermal behavior of murals and their degradation risks before and after cave openings. The key findings are as follows: (1) Open caves amplify the annual temperature fluctuations of murals, most notably in arid regions; (2) Open caves reduce the annual RH (relative humidity) fluctuations, particularly in semi-arid regions; (3) Open caves increase days with excessive daily hygrothermal variations, especially in semi-arid regions; and (4) Open caves raise salt efflorescence risk in humid, semi-humid, and semi-arid regions while reducing it in the arid region. These results offer valuable guidance for the conservation and management of cave relics across varied climates.