In this paper, a new method has been proposed to determine the timing of reducing grain moisture ventilation by specific enthalpy and absolute humidity of air. Specifically, a chart for selecting the timing of aeration for grain drying has been plotted with the air specific enthalpy as the x-axis and the corresponding absolute humidity as the y-axis, by adding lines representing the equilibrium absolute humidity for grain desorption and the allowable range for aeration. This chart can then be used to select the timing of aeration for grain drying. Compared with the commonly used air enthalpy-humidity chart, the proposed chart incorporated the parameters for allowable conditions for grain aeration specified in national industry standards. It visually presented the allowable range for aeration at different grain temperatures, moisture contents, air temperatures, relative humidities, and specific enthalpies, facilitating users in selecting the timing of aeration and conducting related research. This method could effectively assist in ensuring grain storage safety, improving the efficiency of aeration for grain drying, and reducing energy consumption costs.