The estimation of China's future food grain demand has become vital input for designing grain security measures. Addressing the population's age-gender and urban-rural structures under three fertility policies scenarios together with concerns for balanced diets, we established a multifactor driven model to forecast China's food grain demand (including staple food grain and feed grain) during 2021-2050. The three scenarios are as follows; the two-child fertility policy for couples when either the husband or the wife is from a single-child family (scenario 1); universal two-child policy (scenario 2), and no limitations on the number of children (scenario 3). The results show that in scenario 3, China's food grain demand would peak in 2030 at about 329.3 million tons, about 3.7 million tons higher than that in scenario 2, and 104.7 million tons lower than that estimated with the traditional per capita method. These findings indicate that the demographic transition for fertility policy adjustment is not the main impacting factor of China's food grain security from 2021 to 2050. We might overestimate food grain demand by about 15 percent if we ignored each agegender and urban-rural structure of the population. Then it may lead to an oversupply of grain and accumulation of stocks, which would generate about 1 billion RMB annual inventory cost burden. An important complement to the demographic strategy would come from the adoption of the proposed Dietary Guideline for Chinese Residents (2019). It can make people much healthier and save about 7.5 percent of China's food grain consumption, reducing the pressure scarce supplies of water and land in the country.Food security means a sufficient supply of foods and nutrients (FAO,1996), which indicates one needs a diverse, balanced diet containing various foods, such as those rich in vitamins, iron, and zinc. Close to 750 million -or nearly one in ten people in the world in 2019-were exposed to severe levels of food insecurity. The majority of the world's undernourished -381 million -are still found in Asia. At the global level, the prevalence of food insecurity at a moderate or severe level, and severe level only, is higher among women than men. The gender gap in accessing food increased from 2018 to 2019. If recent trends continue, the number of people affected by hunger will be 9.8 percent of the population by 2030, even without considering the potential impacts of the COVID-19 pandemic (FAO, 2020).China is the most populous country and the largest food consumer in the world. During 2013-2019, China's soybean, rice consumption accounted for about 30% of the total