Abstract: Global food security can dominate the balance of grain production in China. Dual challenges can be found in the grain supply security from both internal and external factors. Therefore, it is urgent to clarify the role of cultivated land use in grain production under various circumstances. Previous research has explored the relationship between cultivated land use and grain production. It is still lacking to integrate the regional yield potential and reduction risks into an evaluation of cultivated land in grain production. Current evaluations of cultivated land use also fail to adequately consider the complexities of these new challenges. In this study, the five-dimensional framework (cultivated land quantity stability, quality improvement, ecological sustainability, grain supply potential, and utilization risks) was proposed to evaluate the grain production security of cultivated land use in China. Among them, the traditional "quantity, quality, and ecology" framework was expanded to protect the cultivated land. Two additional dimensions were also introduced: development potential and utilization risks. A multi-scale evaluation was conducted at the regional, provincial, and municipal levels. Finally, the 13 indicators were selected from 2007 to 2022. The results indicate that grain production security was significantly improved during the study period. The overall score increased from 0.46 in 2007 to 0.56 in 2022, indicating a 22% improvement. The Yunnan-Guizhou Plateau region recorded the most substantial growth, with the scores rising from 0.39 to 0.52—a more than 30% increase. In contrast, the Huang-Huai-Hai Plain, the major grain-producing region, showed the smallest improvement, due to its already advanced level of sustainable cultivated land use. Spatially, the superior security of grain production was observed in the regions, such as the Northeast Plain, the Middle and Lower Yangtze River Plain, and parts of the Sichuan Basin and Xinjiang. The scores consistently exceeded the national average of 0.45. Conversely, the Loess Plateau and the Tibetan Plateau displayed weaker capacities, some of which the score was below 0.42. The Sichuan Basin and Xinjiang also exhibited significant potential for grain supply, with potential use scores 1.5 and 1.8 times the national average, respectively. The higher risks of unstable cultivated land use were found in the Loess Plateau and Qinghai-Tibet Plateau, with more than 35% of municipal units with high-risk concentrations. Significant clustering was observed in the spatial distribution of scores over the five dimensions. The patterns of high- and low-value regions varied greatly. Importantly, there was no correlation between grain output and production security, rather than the conventional metrics of grain yield. An emphasis was also put on the regional yield potential and the multifaceted risks—both natural and social—associated with cultivated land use. The evolving dynamics of cultivated land use were effectively captured for grain production. The evaluation was also integrated with the grain yield data. A dual-dimensional approach was obtained to diagnose regional grain security. The spatial differentiation patterns were identified for the decision-making on the grain yield potential. The risk of cultivated land use was reduced to enhance the overall capacity of cultivated land for the high grain security. This evaluation framework of cultivated land use can also provide insights to improve grain production security.