A battery pack, comprising: a lower casing; a plurality of battery modules received in the lower casing, each battery module comprising a shell, the shell comprising: an enclosing frame which has two side walls, a top wall, a bottom wall and a receiving cavity, the receiving cavity being enclosed by the two side walls, the top wall and the bottom wall, and the receiving cavity having openings respectively opened at two ends in a length direction; two end plates respectively securely connected with the two ends of the enclosing frame in the length direction to respectively seal the openings of the receiving cavity; each side wall is formed with a fixing rib protruding outwardly along a width direction, and the fixing rib being provided with at least one through hole passing through the fixing rib along a height direction; and a plurality of fasteners, each fastener passing through the corresponding through hole of the battery module to fix the battery module in the lower casing; characterized in that the lower casing comprises: an enclosing plate composed of four enclosing walls; a bottom plate connected with the enclosing plate; and a plurality of support plates spaced apart from each other and suspended between the two opposite enclosing walls, each support plate is provided with a plurality of fixing holes (fh) extending in the height direction; each battery module is provided between two adjacent support plates, and the fixing rib of each side wall of the battery module laps on an upper surface of the support plate, and each fastener passes through the corresponding through hole of the each side wall and is fixed in the corresponding fixing hole (fh) on the support plate so that the battery module is fixed on the two adjacent support plates. a lower casing; a plurality of battery modules received in the lower casing, each battery module comprising a shell, the shell comprising: an enclosing frame which has two side walls, a top wall, a bottom wall and a receiving cavity, the receiving cavity being enclosed by the two side walls, the top wall and the bottom wall, and the receiving cavity having openings respectively opened at two ends in a length direction; two end plates respectively securely connected with the two ends of the enclosing frame in the length direction to respectively seal the openings of the receiving cavity; each side wall is formed with a fixing rib protruding outwardly along a width direction, and the fixing rib being provided with at least one through hole passing through the fixing rib along a height direction; and an enclosing frame which has two side walls, a top wall, a bottom wall and a receiving cavity, the receiving cavity being enclosed by the two side walls, the top wall and the bottom wall, and the receiving cavity having openings respectively opened at two ends in a length direction; two end plates respectively securely connected with the two ends of the enclosing frame in the length direction to respectively seal the openings of the receiving cavity; each side wall is formed with a fixing rib protruding outwardly along a width direction, and the fixing rib being provided with at least one through hole passing through the fixing rib along a height direction; and a plurality of fasteners, each fastener passing through the corresponding through hole of the battery module to fix the battery module in the lower casing; characterized in that the lower casing comprises: an enclosing plate composed of four enclosing walls; a bottom plate connected with the enclosing plate; and a plurality of support plates spaced apart from each other and suspended between the two opposite enclosing walls, each support plate is provided with a plurality of fixing holes (fh) extending in the height direction; an enclosing plate composed of four enclosing walls; a bottom plate connected with the enclosing plate; and a plurality of support plates spaced apart from each other and suspended between the two opposite enclosing walls, each support plate is provided with a plurality of fixing holes (fh) extending in the height direction; each battery module is provided between two adjacent support plates, and the fixing rib of each side wall of the battery module laps on an upper surface of the support plate, and each fastener passes through the corresponding through hole of the each side wall and is fixed in the corresponding fixing hole (fh) on the support plate so that the battery module is fixed on the two adjacent support plates.