To analyze the cause of the reverse deformation and the effect of different jointcutting measures on the dam deformation and upstream surface stress, this paper takes the turning dam section at the right bank of Danjiangkou Dam as the research object, and carries out numerical simulations with 3-D linear and nonlinear FEM. The dam displacements and stresses under various joint-cutting locations, different numbers and depths are put forward. The computation results show that arch effect caused by the grouting in early stage is the main cause of the reverse deformation of the turning dam section. In order to reduce or eliminate the reverse deformation and improve the upstream surface stress at EL .143 m , it is recommended that joint-cutting measures should be taken, and joint cutting depth should be reached around EL .140 m .