The thermal expansion characteristics of concrete seriously affect the normal construction of agricultural water conservancy projects. Therefore, the modeling and analysis of the thermal expansion characteristics of concrete in the water conservancy project is proposed. The finite element model of thermal expansion of concrete is established. Based on this model, the effect of prestress on the coefficient of thermal expansion of concrete and the influence of prestress of concretes normal section on the thermal expansion of concrete are analyzed. Through the selection of the concrete material unit of the agricultural water conservancy project, and the analysis of the material properties, the thermal expansion characteristics of the concrete section of the water conservancy project are simulated, and the analysis diagram of the thermal expansion characteristics of the concrete section is established to determine the calculation method of the thermal expansion coefficient of the concrete. The experimental results show that the proposed method can accurately calculate the coefficient of thermal expansion of the agricultural water conservancy projects, and the calculation process is relatively simple.