Abstract: As an important part of the reform of financial support for agriculture, rural public investment has played an important role in promoting agricultural development and increasing farmers’ income in recent years. Based on the relevant data from 2003 to 2016, this paper empirically studies the impact of special investment in irrigation and water conservancy on farmers’ income. The results show that: Firstly, under the condition of controlling the relevant influencing factors, the income-increasing effect of irrigation and water conservancy investment is mainly reflected in the increase of farmers’ household operating income, but it is difficult to become a powerful factor driving the overall income level of farmers. Secondly, the investment in irrigation and water conservancy construction squeezed out the financial subsidy or transfer expenditure to farmers to a certain extent, resulting in the income “substitution effect” . The results of heterogeneity analysis show that the income-increasing effect of special investment in irrigation and water conservancy has the characteristics of increasing income and regional differences. On one hand, the increase of income shows a marginal increasing trend, the higher the operating income of farmers’ families, the stronger the income increase effect of irrigation and water conservancy investment. On the other hand, the more dependent on agricultural income, the more significant the income-increasing effect of irrigation and water conservancy investment. The results of this paper show that the income-increasing effect of irrigation and water conservancy investment is not yet saturated, and continuing to increase investment and optimizing the capital structure of irrigation and water conservancy supporting agriculture will help to deepen the reform of financial support for agriculture and promote the balanced development of rural areas in various areas.