The embodiment of the invention discloses a battery charge state determination method and a device, wherein the phenomenon that the charge state goes beyond the normal physical range is reduced. The method comprises the steps of according to the equivalent circuit model of a battery and the Kalman filtering algorithm, obtaining a first parameter value for the relevant parameters of the battery charge state; if the first parameter value is within a preset range, obtaining an optimal solution for the battery charge state at the current moment based on the first parameter value; if the first parameter value is out of the preset range, replacing the first parameter value with a preset second parameter value for the relevant parameters, and obtaining the optimal solution for the battery charge state at the current moment, wherein the second parameter value is within the preset range.