China faces the dual challenge of water scarcity and food security with continued population growth. This paper explores methods to meet that demand without increasing agricultural water usage. The results show that China’s grain yield increased from 1.09 to 5.38 t/ha in 1949–2014 and may reach 6.13 t/ha in 2030. Further, food production increases can be achieved by increasing crop yield and enhancing irrigation efficiency (the ratio of crop irrigation water consumption to water diversion, IE). According to forecast scenarios, future grain yield will reach 5.86 t/ha if the ratio of total irrigated areas increases by 12.3%, while the IE will reach 0.583, lower than the planning goal of 0.600. The increase of water productivity proves that China can ensure its food security by improving IE and expanding irrigation areas with the water that is saved. The basic premise to ensure food security is to ensure that future investments in agricultural water and arable land are not reduced. The future should focus on provinces in the South, which is the major grain-producing area, in developing irrigation. The Northern regions have limited potential to develop irrigation and should therefore maintain the current scale of agricultural production to lay a solid foundation for food security in the future.