Grain storage facilities are an important material carrier of China’s grain security system, and are of great significance for accelerating the high-quality development of the grain industry, maintaining the security and stability of China’s grain industry chain supply chain in the new era, and building a higher-level, higher-quality, more efficient and more sustainable grain security system. According to the characteristics of China's grain production and demand, this paper innovatively proposes a reserve size measurement method based on the amount of surplus grain, overcomes the shortcomings of the disconnection between the reserve size and the output, gives the method of reasonably measuring the scale of storage facilities according to the functions of different links of acquisition, reserve and transit. According to the characteristics of different links, we find out the main determinants of each link as follows: the storage is mainly determined by the amount of commodities, the reserve is mainly determined by the size of the reserve, the transit is mainly determined by the flow of goods. A formula is established through the coefficient analysis, and the reasonable scale of grain storage and logistics facilities is derived. The economic model of the reserve warehouse that optimizes the layout of storage facilities is proposed, that is, the reserve warehouse based on the reserve function has the highest efficiency at a certain scale, and the scale should not be too small or too large. The relevant measurement methods proposed in this paper provide an important reference and basis for the rational planning and construction of grain storage facilities in different regions in the new era.