The objective of this study was to establish a scientific schedule for cave investigation and maintenance that would minimize microclimate fluctuations induced by door openings. To this end, the microenvironment inside and outside Cave 87, a small basal-level cave in the Mogao Grottoes, was monitored and analyzed. The present study systematically analyzed the variation characteristics of the temperature (T), the relative humidity (RH), and the absolute humidity (AH) inside and outside the cave, along with their differentials. The identification of convective patterns between indoor and outdoor air in different seasons and the corresponding moisture absorption-desorption models of the wall paintings was achieved through curve fitting and equation solving for the temperature and RH differences between the interior and exterior. Furthermore, an investigation was conducted into annual variations in dew point temperature. A mixed linear model for the comparison of interior and exterior temperature was developed, indicating that for every 1 ℃ increase in external temperature, there is an increase of 0.395 ℃ in the internal temperature. The extreme and zero-value dates of temperature and humidity differences between the interior and exterior were determined. The findings indicate that the optimal periods for cave investigation and maintenance are March, April, September, and October. Conversely, opening the door during winter and summer increases the risk of moisture condensation inside the cave. These findings offer significant insights for the preventive conservation of wall paintings in Cave 87 and provide theoretical support for the optimization of protection strategies in analogous caves.