Grotto cultural heritage sites, represented by the Mogao Caves in Dunhuang, are important sites in China. However, under the action of evaporation, salt crystallization of the salt solution contained in the rock leads to serious damage to grotto murals and other cultural relics. This study examines the transport and crystallization mechanisms of salt solution in grotto environments. Through theoretical and numerical simulations, we investigated the competitive coupling between salt solution transport and crystallization and the evolution of the spatial distribution of salt concentration. Environmental factors such as ambient temperature, air relative humidity, and wind speed were numerically investigated to determine the critical conditions for salt crystallization. This study considers a combination of environmental control factors necessary to prevent salt crystallization, thus providing a theoretical and operational basis for the protection of related cultural relics.