Damage of prefabricated canal members is common in construction period，so it is urgent to improve the structural bearing capacity of components.Taking prefabricated U-shaped grooves as the research object，the stress characteristics of components construction period are analyzed，and the stress state of components is analyzed by material mechanics and finite element method.If the maximum tensile stress exceeds the ultimate flexural strength of concrete，brittle failure of components occurs.The damage mechanism of components is explained from the perspective of concrete materials.At the same time，some optimization suggestions are put forward for the structure of components such as increasing the local thickness of groove bottom or increasing concrete strength grade.It's a good way to reduce the maximum tensile stress and increase concrete ultimate flexural strength.The actual bearing capacity of component structure could be further enhanced，which is helpful to improve the quality of farmland water conservancy projects.