The invention relates to a connection failure judging and protecting method of power cell boxes as well as protecting system and device. The judging method comprises the following steps of: collecting temperatures of positive and negative poles of all cell boxes; carrying out absolute temperature judgment on the temperatures; and if an absolute temperature judgment basis is satisfied, judging that the connection of the cell boxes has a failure; carrying out relative temperature judgment; and if a relative temperature judgment basis is satisfied, judging the connection of the cell boxes has a failure; and when the absolute temperature judgment basis and the relative temperature judgment basis are both not satisfied, judging that the connection of the power cell boxes is normal.