Biomass storage is essential for effective utilization of lignocellulosic biomass. Although long-term storage of biomass is as important as the conversion process, no effective method has been developed. This study investigated the effects of low-moisture anhydrous ammonia (LMAA) pretreatment on biomass quality for long-term storage with moisture content from 30 to 70 %. Carbohydrate loss due to fungal growth was observed in the moisturized corn stover without ammonia loading, after 12 weeks of storage. This also resulted in reduced enzymatic digestibility. Both ammoniation and LMAA pretreatment reduced the decomposition of carbohydrates by fungal growth, during storage in the presence of moisture. LMAA pretreatment rendered 83 % of glucan and 67 % of xylan digestibility after 24 weeks of storage. Ammoniated corn stover also resulted in 63 % of glucan and 48 % of xylan digestibility at 0 week of storage, and hydrolysis yields increased to 78 % for glucan and 64 % for xylan, without pretreatment, after 12 weeks of storage.