Abstract: The value of the flywheel torque of the super large unit has an important influence on the adjustment guarantee parameters and the stability of the system. In this paper,a simulation model is established based on an example of a hydropower station project in a high-altitude area to study the relationship between the value of the flywheel torque of the unit and the closing laws of different guide vanes. The results show that when the guide vane selects the straight-line closing rule,the flywheel torque of the super large unit has a minimum critical value under the control of the increase in speed;under the broken-line closing rule,the minimum pressure of the draft tube inlet of the power station in high altitude areas is restricted by the specification constraints and the value of the flywheel torque is also limited.