Abstract: The Huang-Huai-Hai region in China faces severe water shortages, with excessive groundwater consumption posing a significant obstacle to its economic and social development. This study utilizes GRACE gravity satellite data and GLDAS land surface assimilation data from 2003 to 2021 to analyze and evaluate variations in groundwater storage in the Huang-Huai-Hai region. Statistical methods are employed to examine the spatiotemporal characteristics of these variations, and the factors contributing to changes in groundwater storage, including precipitation, evapotranspiration, groundwater supply, and inter-basin water diversion, are investigated. The results reveal that 94.2% of the Huang-Huai-Hai region experiences a decline in groundwater storage, with an average rate of −1.22 cm/a. The Haihe River Basin exhibits a rate of 1.75 cm/a, the Huaihe River Basin experiences a rate of −0.57 cm/a, and the below Huayuanko area of the Yellow River Basin has a rate of 2.11 cm/a. The spatial pattern of groundwater storage indicates increasing decline rates from south to north. The dominant factors influencing groundwater storage variations differ among the three basins. Precipitation has a greater impact on groundwater storage in the Huaihe River Basin compared to the Haihe River Basin, while long-term groundwater supply reduction contributes to the decline in groundwater storage in the Haihe River Basin and below Huayuankou area of the Yellow River Basin. The increasing inter-basin water diversion in recent years has led to a reduction in groundwater supply in the Haihe River Basin, alleviating the declining trend of groundwater storage. Additionally, groundwater storage in the below Huayuankou area of the Yellow River Basin has experienced rapid growth since 2020.