As a promising material for bioethanol production, corn stover has been studied under various pretreatment methods prior to production of bioethanol. However, the storage of pretreated corn stover is still challenged by both weather conditions and the physical properties of its own. The objective of this experiment is to evaluate the effect of low-moisture anhydrous ammonia (LMAA) pretreatment method on biomass quality during long periods of storage. In this study, corn stover was contacted with various ammonia loadings (0, 0.1, and 0.2 g/g DM biomass) and moisture content (20 wt.%, 40 wt.%, and 60 wt.%) from 1 day to 90 days both in sealed and open containers. As a result, the mass loss in sealed container increased with time; however, the mass loss in open container was affected by the conditions of the environment. In terms of the carbohydrate, no significant reduction was observed in either sealed or open containers.