Abstract: The study used life cycle assessment (LCA) methodology to calculate environmental impacts of producing 1 kg of corn and 1 kg of alfalfa for animal feed, from agricultural raw materials, including cultivation and other aspects of on farm production and associated transport. Data used are for the years 2014 and 2015. The calculation predicts how structural adjustment to crop production patterns will affect China’s environment. In addition, the life cycle environmental impact differences between production of 1 food equivalent unit (FEU) of corn and alfalfa were compared with calculations based on protein and energy content. It was found that life cycle environmental impacts of 1 kg of corn and 1 kg of alfalfa, respectively, were 9.35 and 1.22 MJ of primary energy demand (PED), 889.33 and 144.37 kg of water use (WU), 0.13 and 0.02 kg antimony-eq of depletion of abiotic resources (DAR), 1.21 and 0.10 kg CO₂-eq of global warming potential (GWP), 4.23 and 0.19 g PM_2.5-eq of respiratory inorganics (RI), 2.41 and 0.17 g NMVOC-eq of photochemical oxidant formation potential (POFP), 0.00855 and 0.00080 kg SO₂-eq of acidification potential (AP), 1.20 and 0.09 kg P-eq of freshwater eutrophication potential (FEP), and 0.0126 and 0.0015 CTU of ecotoxicity. Meanwhile, life cycle environmental impacts of 1 FEU alfalfa compared to corn are: PED 20.50%, WU 25.43%, DAR 21.08%, GWP 12.99%, RI 6.98%, POFP 11.15%, AP 14.76%, FEP 12.31%, and ecotoxicity 18.58%. In view of the ecological and economic superiority of alfalfa, subsidies no less than those for other grains should be given. Moreover, agricultural reform such as shifting corn production to alfalfa, cannot only help meet China’s food requirements internally, but also is a convenient and economical way to reduce the resource consumption and environmental pollution in agricultural production. This study provides a scientific basis for a policy to shift from grain to forage production in China.