Abstract: As an important breakthrough in the modernization and transformation of plateau characteristic agriculture, the assessment of the effect of coffee industry policy has theoretical value and practical significance in optimizing the implementation path of rural revitalization. Based on the “one county one industry” policy implemented in Yunnan Province in 2019, this paper conducted a natural experiment, and a double-difference model based on the county data of the four major demonstration areas from 2010 to 2023, systematically examined the income-generating effect of the coffee industry policy on farmers’ incomes and its functioning mechanism. The results of the study showed that: the implementation of the policy significantly promoted the growth of farmers’ income in the counties, and had a significant and robust effect on the per capita disposable income of farmers; there was a regional heterogeneity in the income-generating effect of the policy of “one county one industry” , i.e., the effect of farmers’ income-generating effect in the regional areas was significantly stronger than that in the counties; and the policy of “one county one industry” had a significant impact on the income of farmers. The “one county one industry” policy promoted farmers’ income growth by providing policy support and financial inputs that meet farmers’ needs. For this reason, the policy system should be further improved, the policy orientation clarified, the implementation of the policy improved, and the tilting of the policy emphasized, so as to promote the growth of farmers’ incomes in the pilot demonstration counties of the “one county one industry” policy.