The invention relates to the technical field of automatic voltage control of power systems, in particular to a method for designing coordinate amount among automatic voltage control systems of a power grid and an implementing method thereof. The coordinate amount represents the voltage areal control deviation and consists of boundary node voltages among the automatic voltage control systems in different area and on different levels and weighted sum of reactive disturbance injected into a local area from foreign areas. In the invention, whether reactive disturbance occurs in or out the area can be determined through the coordinate amount, the direction and size of the reactive influences on neighboring areas of the control action of the local area are measured, each control area only responds for the reactive disturbance in the local area, and the examination is fair; and thus, the areal control responsibility is clear, coupling is reduced and coordinate control can be realized.