Abstract: High-standard farmland construction is crucial for the overall development of agricultural modernization. It serves as the “stabilizer” for food security and the “golden key” for increasing farmers’ income. Based on panel data from 31 provinces (cities, regions) across the country from 2005 to 2023, this study evaluates the impact of high-standard farmland construction policy on farmers’ income and its mechanism of action using the intensity difference-in-differences model. The findings indicate that the high-standard farmland construction policy significantly promotes the income increase of local farmers. The heterogeneous analysis results show that the policy has a non-equilibrium effect on farmers’ income. The income-increasing effect is more pronounced in areas with low labor transfer, high agricultural disaster rates, and low rural human capital. The mechanism test indicates that the high-standard farmland construction policy mainly promotes the income growth of local farmers through agricultural mechanization and large-scale agricultural operations. The synergy between the two endows the policy with a self-fulfilling mechanism for increasing farmers’ income. The extended analysis shows that the high-standard farmland construction policy has a “Matthew effect” of widening the income gap among farmers, but its intensity is weaker than the overall income-increasing effect. The above conclusions provide insights for the optimization of high-standard farmland construction policies and the improvement of common prosperity policies.