Temperature and moisture content are two important physical variables that play a considerable role in the study of quality changes during grain storage. Ventilation is used to cool the grain pile and keep the temperature constant to prevent moisture migration. Good ventilation conditions have a significant impact on the storage safety in the granary. At present, the research on the influence of relative humidity of ventilation air on the moisture of the grain reactor is relatively rare. The changes of grain temperature and moisture during ventilation caused by different inlet air relative humidity were explored and compared by a combination of numerical simulation and experimental research in this paper. According to the results, the cooling and drying efficiency is higher when the relative humidity of the inlet is lower, which makes the wheat grain pile cool more quickly and keeps the activities of insects and molds at a lower level.