The amount of food loss caused by condensation in the storage process during the post-harvest period in China is huge. Seasonal alternation is an important factor in causing condensation on grain bulk. The areas which are prone to condensation during winter-spring alternation are found out and early warned by analyzing the temperature and humidity data of the granary and the graph, and the relationship between the dew point and the temperature and humidity. It provides a theoretical basis for improving China's grain monitoring system, guiding the practice of grain storage and ensuring food security.