Abstract: 【Objective】 This paper assesses the carbon footprint and water footprint of major food crops in the northwest region, and establishes a multi-objective planting structure optimization model based on the carbon footprint and water footprint to adjust the spatial distribution of food crops in each province, providing a theoretical basis for reducing carbon emissions and enhancing water resource management. 【Method】 Based on the planting area, yield, and agricultural inputs of wheat, maize, and rice in the northwest region, the carbon footprint was evaluated using Life Cycle Analysis (LCA); Based on evapotranspiration and effective precipitation, the water footprint is evaluated by Penman-Monteith formula; Multi objective optimization of the layout of three major grain crops in the five northwest provinces based on entropy weight method. 【Result】 The data showed that the carbon footprint and water footprint of wheat, maize and rice in northwest China from 1999 to 2020 showed significant differences in different provinces. The carbon emissions from the production of three grain crops, wheat, maize and rice, in the northwest region show a distribution pattern of higher levels in the eastern and western regions and lower levels in the central region; The range of carbon footprint per unit production (PCF) is 0.36-0.63, 0.33-0.56, 0.57-0.97 t CO₂-eq·t^-1; The carbon footprint per unit area (FCF) is (2.46±0.77), (3.21±0.49) and (5.57±0.91) t CO₂-eq·hm^-2, respectively. From 2010 to 2018, the total green water content of wheat, maize and rice in the northwest region showed a steady upward trend, with regions with higher average green water content distributed in Shaanxi, Gansu, and Ningxia. The total amount of blue water showed an upward trend from 2010 to 2015, and a downward trend from 2015 to 2018. The regions with higher average total blue water were distributed in Gansu, Ningxia, and Xinjiang. Among the three major grain crops in northwest China, maize consumes the least blue water footprint, with an average blue water footprint of 0.45 m³·kg^-1; The blue water footprint consumption of rice is the largest, and the average production blue water footprint is 0.77 m³·kg^-1. Based on the carbon footprint and water footprint, optimize the planting structure of food crops, using different crop planting areas in different provinces as decision variables and set optimization scenarios focusing on reducing carbon emissions and increasing green water use efficiency according to different weights. In Scenario 1, the total carbon emissions decreased by 1.9% and the total green water increased by 5.0%; In scenario 2, the total carbon emissions decreased by 11.8%, while in scenario 3, the total green water emissions increased by 6.7%.【Conclusion】There are significant spatiotemporal differences in carbon emissions and total water content among the three major grain crops in the northwest region. Under the premise of ensuring food crop safety, increasing the planting area of wheat (7.1%), reducing the planting area of maize (5.5%), and rice (8.7%) has resulted in certain improvements in economic, resource, and ecological benefits. Under certain social equity conditions, optimization can improve the utilization of green water resources, reduce carbon emissions, and alleviate environmental pollution.

Key words: carbon footprint, water footprint, optimization of planting structure, food crops, Northwest region