The invention discloses a segmented setting method for a frequency deviation coefficient of an automatic power generation control system. The method comprises the following steps: calculating a natural frequency characteristic coefficient of a power grid in an offline manner through a whole-process dynamic simulation program of a power system, finding out a curve inflection point corresponding toa starting threshold value of a frequency modulation function of a direct-current system, and segmenting a system frequency deviation coefficient of automatic power generation control. The frequency deviation coefficient is matched in real time according to the actual frequency deviation of the power grid during the automatic power generation control of the provincial control area, and the adjustment demand of the control area is calculated. In a power grid frequency recovery process after a power grid fault, the frequency deviation coefficient changes along with the change of the frequency fed back by the frequency modulation function of the direct-current system, thereby achieving the coordination and cooperation of automatic power generation control and the direct-current frequency modulation function after the power grid breaks down, and guaranteeing the accurate control of the automatic power generation control system and rapid recovery of the power grid frequency after the powergrid breaks down.