The active participation of farmers is not only a real demand to alleviate the dilemma of “free-rider” in improving the rural living environment but also a requirement of the Times to realize ecological sustainability and rural revitalization. The planning behavior theory tells us that improving farmers’ willingness is an important prerequisite for farmers’ activities. This paper constructs the analysis framework of “organizational support (government and village committee) → environmental health literacy → farmers’ willingness” from the actual practice of government-led rural living environment improvement. Using data from a sample of 1225 farmers in Gansu Province and Jiangsu Province, China, we empirically tested the mechanisms of organizational support on farmers’ willingness to participate in living environment improvement and the mediating effect of environmental health literacy using formative structural equation modeling. The study showed that organizational support positively affected farmers’ willingness to participate, the effect of emotional support was more potent than that of instrumental support, and there were regional differences in the relative effects of government support and village committee support on farmers’ willingness to participate. All four types of organizational support positively affected environmental health literacy, but the degree of the effect differed and showed regional heterogeneity. Among the direct effects of farmers’ environmental health literacy on their willingness to participate, basic skills made the highest contribution, followed by basic ideas and the lowest basic knowledge. Among the indirect effects, basic skills made the most significant contribution in the pathway of organizational support to increase farmers’ willingness to participate through fostering farmers’ environmental health literacy. The results can provide a theoretical basis for government and village committees to policy optimization and improve the system, improve the resource utilization of the government and village committees, improve farmers’ environmental health literacy, and change farmers’ participation attitude.