Abstract: The farming-pastoral ecotone in northern China is the climate intersection zone between the semi-humid region and the semi-arid region. The adjustment of agricultural structure is an eternal theme in the process of agricultural economic development. From the perspective of reducing carbon emission and increasing carbon sink， and based on ecological priority development， opportunity cost， externality， law and economics， Pareto optimality and other theoretical basis， this paper used carbon emission model， carbon absorption model， decoupling model and other methods to make an empirical analysis of the carbon emission of farmland ecosystem， carbon uptake of crops per unit area， and the decoupling relationship between carbon emission and agricultural output value. The research conclusion showed that to achieve the purpose of reducing carbon emission， enhancing carbon sink function and developing agricultural economy， the studied areas need to adjust and optimize agricultural structure. In addition， in view of the problems such as increasing opportunity cost， direct economic loss and positive externalities caused by agricultural structure adjustment， this paper puts forward the suggestion of building the legal system of agricultural structure adjustment to stimulate and regulate the agricultural structure adjustment behavior through macro-control and market regulation.

Key words: Carbon reduction perspective, Northern farming-pastoral ecotone, Structural adjustment of agriculture, Rule of law system

摘要： 北方农牧交错带是半湿润地区与半干旱地区的气候交汇带，该区域农业结构调整是农业经济发展过程永恒的主题。文章基于降低碳排放，增加碳汇的视角，依据生态优先发展、机会成本、外部性、法经济学、帕累托最优等理论基础，利用碳排放模型、碳吸收模型、脱钩模型等方法对农田生态系统碳排放、单位面积农作物碳吸收量，以及碳排放量与农业产值脱钩关系进行了实证分析。研究结论显示研究区为了达到降低碳排放、增强碳汇功能、发展农业经济的目的，需要进行农业结构调整与优化，并针对农业结构调整可能增加机会成本、产生直接经济损失、存在正外部性等问题，提出构建农业结构调整法治体系对农业结构调整行为进行激励、宏观调控与市场规制的建议。

关键词: 减碳视角, 北方农牧交错带, 农业结构调整, 法治体系