The invention discloses a method and a device for estimating the SOP of a battery system, which may effectively track the OCV change and impedance change under the current operating conditions of the battery system based on the amount of lithium intercalation in multiple predetermined positions in the active material in the battery of the battery system in the current operating condition, thereby determining the first dynamic correspondence between OCV and SOC under the current operating condition and the second dynamic correspondence between impedance and SOC.