Abstract: Understanding the mechanism and the constraints of the impacts of the development of agricultural producer services on farmers’ income growth is of great significance to the improvement of agricultural producer service, the transformation of agricultural technology progress and the increase of farmers’ income. Based on a provincial panel data from 2009 to 2018, this paper analyzed the logical relationship among agricultural producer services, agricultural technology progress, and farmers’ income growth by the mediation effect model and the panel threshold model with the land scale per capita as the threshold variable to verify the nonlinear impacts of agricultural producer services on the growth of farmers’ income. Results show that agricultural producer services and agricultural technology progress have some positive impacts on farmers’ income and both of which have stronger effects on wage income than on agricultural income. Agricultural technological progress is the intermediary variable between agricultural producer services and farmers’ income, and the intermediary effect is 4.5%. The intermediary role of agricultural technological progress in the main grain consumption regions is the largest, which is far higher than that in the main production regions and the production and consumption balance regions. Technological progress through agricultural producer services is easier to increase agricultural income than wage income. In general, the effects of agricultural producer services on the growth of farmers’ income are nonlinear. With the expansion of land scale per capita, the marginal effects of agricultural producer services on the growth of farmers’ total income and wage income present an increasing trend, while the promotion effect of services on agricultural income is not affected by the land scale. Especially in the main production regions, when the scale of land exceeds certain threshold, it is more conducive to increase the promotion degree of agricultural producer services to farmers’ income. Therefore, this paper provides some policy suggestions, including: 1) focusing on developing agricultural producer services in main grain production regions and the production and consumption balance regions; 2) paying more attention to and giving full play to the ability of agricultural producer services to promote the transformation of agricultural technological progress into productivity; 3) strengthening the technical support of services, especially the introduction of labor substitution technology; and 4) alleviating the restriction of more people and less land on the full play of agricultural producer services through the land circulation, land trusteeship and some other scale management patterns.