In this study, the computable general equilibrium (CGE) model was used to deeply study the optimization problem of water-energy-grain-land correlation in China. In the process of building the model, the correlation among water resources, energy, grain and land and the actual situation in China were fully considered, and the sub-modules of agriculture, energy and water resources were optimized and improved. It is found that the correlation among water resources, energy, grain and land has an important impact on China’s economic growth and environmental protection. Under the current policy, there is a certain degree of irrationality and optimization space in the relationship between water, energy, grain and land in China. Through policy adjustments, optimized water resource allocation, enhanced energy utilization performance, and restructuring of the agricultural industry, coordinated development among water, energy, grain, and land can be promoted, contributing to improved overall economic efficiency and environmental sustainability in China. Specifically, optimizing the allocation of water resources can reduce the cost of agricultural water use, improve the effect of agricultural water saving and ensure food security; Improving energy efficiency is helpful to reduce energy expenditure and environmental pollution, and at the same time provide more clean energy for agriculture; Adjusting the agricultural industrial structure and developing water-saving agriculture and ecological agriculture are conducive to improving the utilization performance of land resources and ensuring the sustainable development of grain production. This study provides theoretical basis and policy suggestions for the optimization of water-energy-grain-land correlation in China and is of great significance to realize the green and sustainable development of China’s economy.