Food security in China from 1980 to 2017 was studied to understand the factors affecting it. The researchers looked at different scales (city, province, country) and found that food security varied more at smaller scales. They used a food security index based on grain yield, population, and GDP to analyze the changes over time. The main factors influencing food security differed at each scale: tertiary industry was important at the city level, while agricultural output value was key at the provincial and national levels. This research helps identify areas with food security issues and can guide decisions to improve regional food security.