Environmental temperature and humidity are key factors to consider in the fight to protect cultural relics.This work presents research carried out to monitor the temperature and humidity of sealed and open caves in the northern area of the Mogao Grottoes (cave no.132). The effect of sealing on the caves’ temperature and humidity could thereby be deduced. By actively condensing the vapor present, the main sources of water in the caves could also be determined.In open caves, the temperature and humidity changes as the external atmosphere varies. The difference between the daily temperatures inside the open cave compared to that of the outside is relatively small.Wet weather significantly affects the cave’s humidity. Temperature and humidity in the cave are therefore mainly controlled by the outside weather variations.Sealing the cave effectively eliminates the influence of these daily fluctuation. Sealing leads to an apparent increase of the humidity of the air in the cave, which indicates that water vapor arising from the surrounding rock must be entering the caves. A cave sealed for a long time has a relative humidity sufficiently large to activate salt movement, which will cause harm to the murals.However, installation of a condensationdehumidification temperaturehumidity control system in a sealed cave can control the temperature and humidity quite effectively. The condensed water collected in the cave validates the presence of the water vapor sources in surrounding rock. The research presented provides new ideas for exploring the ways of protectinga cave’s cultural relics.