Based on the new requirements and tasks of building an agricultural power, ensuring grain security at a high level is the primary issue for building a large powerful agricultural country with Chinese characteristics. It determines whether the foundation of a large powerful agricultural country is solid. This article explains the connotation and significance of ensuring grain security from the perspective of an agricultural power, clarifies the practical foundation of grain security for China, identifies the problems and challenges faced by maintaining high-level grain security, and finally proposes some policy suggestions. Results show that the requirements for ensuring grain security from the perspective of an agricultural power are multi-level, including total quantity security, quality improvement, structural optimization, ecological sustainability, and supply diversification. Since the reform and opening up, China has made tremendous achievements in various aspects, including grain production capacity, production efficiency, the construction of production and operation system, reserve capacity, and the construction of the logistics system. However, China’s grain security still faces some problems and challenges such as a large gap in total grain production, increased constraints on natural resources, great difficulty in increasing unit yield, continued decline in grain production efficiency, increased import uncertainty, and food waste, etc. In the new era, this paper suggests: to ensure grain security at a high level, to promote the construction of an agricultural power by ensuring grain security as the first priority, continuously to improve grain production capacity, to enhance the resilience of the food supply chain, and to diversify the food supply system.