Establishing a modern grain industry system is a powerful measure to maintain the national grain security and an effective way to adapt the main contradictions in the new socialist era and improve the quality of industrial development. Based on the development characteristics, main contradictions, social needs and industrial laws of the new socialist era, this paper studied the basic framework and composition of the modern grain industry system. This study showed that the main characteristics of the modern grain industry system are the modernization of the industrial chain, the high efficiency of supply chain, the advanced value chain, and the efficient coordination of all links of storage, transportation, processing and marketing. It is pointed out that the goal of building a modern grain industry system is to form a modern grain industry development mode with multi-elements, whole chain, multi-level, toughness and sustainability. The development path of modern grain industry system includes four aspects: the construction of modern grain reserve system, modern grain processing system, green and low-carbon logistics system, and modern science and technology support system. On this basis, the research put forward several policy suggestions such as to deepen the supply side structural reform, accelerate the construction of a unified grain circulation market, improve the stability and systematisms of industrial policies, and promote the digital transformation for the construction a modern grain industry system.