A battery module assembly having unit modules, each of which is configured to have a structure in which unit cells are loaded on a cartridge in a state in which the unit cells are electrically connected to each other via busbars, the battery module assembly comprising: two or more sub-modules arranged in a lateral direction while being spaced apart from each other, each of the sub-modules comprising two or more unit modules that are stacked in a height direction from a ground; a battery management system mounted in a space defined between the sub-modules, the BMS being provided at one side thereof with communication terminals (231, 232); a base plate on which the sub-modules and the BMS are loaded; side cover plates mounted at sides of the sub-modules; a top cover plate loaded on top surfaces of the sub-modules, the top cover plate being coupled to the sub-modules and to the side cover plates by fastening; and a front cover plate mounted at fronts of the sub-modules, the front cover plate being coupled to the sub-modules, the base plate, and the side cover plates, the front cover plate being provided with through holes, through which the communication terminals (231, 232) are exposed, and wherein the cartridge is provided at opposite sides thereof with protrusions, each of which has a fastening hole, and cartridges are coupled to each other so as to constitute each of the sub-modules by inserting cartridge fastening members through the fastening holes, the BMS is configured to have a hexahedral structure, and the communication terminals (231, 232) are mounted to the front cover plate in a state of being exposed from the front cover plate and protrude from an upper end and a lower end of one surface of the hexahedral structure, and the sub-modules are connected to each other via a sub-module fastening member, the sub-module fastening member extends between the upper communication terminal and the lower communication terminal of the BMS, and one surface of the BMS at which the sub-module fastening member extends is depressed such that the sub-module fastening member is mounted in the depression. two or more sub-modules arranged in a lateral direction while being spaced apart from each other, each of the sub-modules comprising two or more unit modules that are stacked in a height direction from a ground; a battery management system mounted in a space defined between the sub-modules, the BMS being provided at one side thereof with communication terminals (231, 232); a base plate on which the sub-modules and the BMS are loaded; side cover plates mounted at sides of the sub-modules; a top cover plate loaded on top surfaces of the sub-modules, the top cover plate being coupled to the sub-modules and to the side cover plates by fastening; and a front cover plate mounted at fronts of the sub-modules, the front cover plate being coupled to the sub-modules, the base plate, and the side cover plates, the front cover plate being provided with through holes, through which the communication terminals (231, 232) are exposed, and wherein the cartridge is provided at opposite sides thereof with protrusions, each of which has a fastening hole, and cartridges are coupled to each other so as to constitute each of the sub-modules by inserting cartridge fastening members through the fastening holes, the BMS is configured to have a hexahedral structure, and the communication terminals (231, 232) are mounted to the front cover plate in a state of being exposed from the front cover plate and protrude from an upper end and a lower end of one surface of the hexahedral structure, and the sub-modules are connected to each other via a sub-module fastening member, the sub-module fastening member extends between the upper communication terminal and the lower communication terminal of the BMS, and one surface of the BMS at which the sub-module fastening member extends is depressed such that the sub-module fastening member is mounted in the depression.