The invention relates to a method for determining the high temperature aging time of a lithium ion battery, which is characterized in that a battery core is taken out from aging equipment and cooled at a preset time interval from aging of the battery core, and a discharge direct-current internal resistance DCR value of the battery core is measured after cooling; the measured DCR value is analyzed, and the time during which the DCR increases and then starts to be stabilized is selected to act as the high temperature aging time of the battery cores of the same system. It is showed that the battery core completes SEI membrane reforming and restoring when the DCR of the battery core does not change or becomes obviously small in change, and the battery core reaches a stable state. The battery core aging time selected according to the method can ensure the aging quality of the battery core, and the aging efficiency of the battery core is improved.