Agricultural carbon emission reduction is indispensable to the achievement of the "double carbon" goal, and the multidimensional relationship network has become the key to the decision-making of farmers' carbon emission reduction behaviour. Based on the perspective of heterogeneous relationship subjects, this paper divides the relationship network into three dimensions: market relationship, government relationship, and social relationship network, and explores the theoretical analysis of the influence of multidimensional relationship network on the decision-making of carbon emission reduction behaviours of farmers, and analyses the mechanism of relationship network influencing the carbon emission reduction behaviours of farmers from the three aspects of information flow, demonstration effect, and factor guarantee based on the social capital theory to lay a solid theoretical foundation for the later empirical analyses. It lays a solid theoretical foundation for the later empirical analysis.