Abstract: Against the backdrop of promoting high-quality agricultural development and sustaining the increase in farmers’ income, whether and how the improvement of agricultural total factor productivity affects farmers’ income has become an important question that urgently needs to be answered. Based on the panel data of prefecture-level cities in Gansu Province from 2013 to 2023, this paper adopts a two-way fixed effects model to systematically examine the impact of agricultural TFP improvement on farmers’ income growth from the perspective of long-term technological progress accumulation. The research conclusions are further verified through robustness tests, heterogeneity analysis, and mechanism tests. The research results show that: firstly, agricultural TFP has a significant positive effect on farmers’ income, and this conclusion remains robust after changing model settings, adding control variables, adopting different standard error estimation methods, and excluding special city samples; secondly, the impact of agricultural TFP on farmers’ income is significantly heterogeneous, and its income-increasing effect is mainly reflected in agricultural income channels, while the direct impact on non-agricultural income is not significant; thirdly, agricultural TFP can significantly improve agricultural labor productivity, thus providing important potential mechanism support for the growth of farmers’ income. The research conclusions of this paper provide useful empirical evidence and policy implications for promoting sustained income growth of farmers and driving high-quality agricultural development through improving agricultural TFP.