The invention relates to a method for determining a total reactive power control capability of a grid-connected point in a wind farm, belonging to the technical field of automatic voltage control of an electric power system. The method comprises the following steps of defining five states of the voltage of a wind turbine end, using the sensitivity of the reactive power to the voltage aiming at the different states of the voltage at the wind turbine end to calculate the total reactive power control capability of the grid-connected point in the wind farm. The method provided by the invention can be integrated in an automatic voltage control substation which runs at the site of the wind farm, thus, the system can take the voltage state of the wind turbine end into account, and the total reactive power control capability of the grid-connected point in the wind farm can be more accurately calculated, and moreover, the control capability can be uploaded to an automatic voltage control master station at a power grid control center.