Cracks are harmful to the usability, durability and safety of hydraulic structure, so accurately predicting the cracking risk is necessary in controlling cracks. In this paper, the model of surge tank structure was built by nolinear finite element program, and the displacement and stress of concrete structure based on the nonlinear constitutive model was discussed. The results according to the linear and nonlinear constitutive model is consistent. However, it’s more useful to study the crack resistance of concrete by nonlinear constitutive model. So we advise to use the nonlinear constitutive model.