To further understand the uplift deformation phenomenon that occurs at the left bank slope near the dam of Xiangjiaba Hydropower Station, hydro-mechanical coupling numerical tests were used to study the mechanism of rock mass expansion and deformation. Based on the hydro-mechanical coupling analysis, the uplift deformation process was simulated. The spatial distribution of the deformation was obtained and the control effect of the pressure relief holes on the uplift deformation was evaluated. The results indicate that the volume expansion strain of the rock mass increases with the permeability coefficient and decreases with the increase of deformation modulus. The initial stress has little effect on uplift deformation. Variation of the seepage field is the direct cause of uplift deformation and the uplift deformation is also the result of the interaction between seepage field and stress field. It is reasonable to use hydro-mechanical coupling theory to reveal the uplift deformation mechanism. Deep drainage holes for pressure relieving are effective for the controlling of the uplift deformation.