In practical engineering, tail water emergency sluice gate is closely linked to sluice gate slots in a pumped storage power station. Under the action of water pulsation, they interact with each other and form a new system. In order to study the influencing mechanism of sluice gate slots on tail water emergency sluice gate, the fluid-structure coupling numerical simulation of a sluice gate in a large pumped storage power station was carried out by ANSYS Workbench. Two kinds of water flow field models were constructed with the consideration of the presence or absence of gate slots. Subsequently, the changes of physical characteristics such as flow field pressure, velocity, stress and displacement of gate components in the fluid-structure coupling model with and without gate slots were studied under eight different gate opening degrees (10%-80%). The results show that the equivalent stress and displacement of the gate decrease gradually with the increase of sluice gate opening. In addition, even a slight change in opening can cast a significant impact on the stress and deformation parameters of the gate. The existence of the gate slot significantly affects the pressure and velocity distribution in the flow field, resulting in the distribution change of the low pressure area, the increase of flow velocity and the aggravation of fluid stratification. When considering the sluice gate slot model, the maximum displacement and stress of each component of the sluice gate are significantly greater than that without considering the sluice gate slot model. The sluice gate-gate slot system model can accurately and comprehensively evaluate the dynamics characteristics of the emergency sluice gates with high water head in pumped storage projects.