Tomb murals hold significant cultural value but are vulnerable to deterioration due to fluctuating hygrothermal conditions, which can lead to issues such as powdering and flaking caused by the salt crystallization-dissolution cycle. Effective environmental control is crucial for heritage preservation. Shunling Tomb built a thousand years ago for an emperor and spanning 26.7 m in length, experiences significant condensation in summer and severe salt crystallization in winter. These issues are likely caused by microclimate changes inside the tomb, primarily driven by air exchange at the entrance. This study develops a coupled heat and moisture transfer model for Shunling Tomb to evaluate how air exchange rates and the hygrothermal properties of incoming air affect the indoor microclimate and associated risks of deterioration. The simulation results show that various environmental control measures, including reducing the air exchange rate, controlling the relative humidity of incoming air, and closing doors, effectively reduce temperature and humidity fluctuations, thereby reducing the risk of salt crystallization in winter and condensation in summer. In particular, closing the door has the most significant effect, reducing the risks of summer condensation and winter salt crystallization by over 90%. However, these measures also increase the risk of microbial growth, emphasizing the need to combine sterilization treatments and environmental control measures for effective tomb conservation. These findings offer practical solutions for preserving Shunling Tomb and serve as a scientific reference for the conservation of similar tombs.