The invention relates to an automatic gas distribution device for a gas cylinder and a using method of the automatic gas distribution device, and belongs to the technical field of methods and equipment for filling a pressure container with liquefied, cured or compressed gas. The automatic gas distribution device comprises a rack, an electronic scale, a PLC control unit, and a vacuum pump mounted on the rack, wherein a gas cylinder weighing mechanism, a gas cylinder fixing mechanism, a gas cylinder filling clamp, a gas cylinder clamp lifting frame and a cylinder valve hand wheel opening-closing mechanism are sequentially arranged on one side of the rack from the bottom up; the electronic scale is positioned below the gas cylinder weighing mechanism; the gas cylinder filling clamp is arranged in the gas cylinder clamp lifting frame; the cylinder valve hand wheel opening-closing mechanism is mounted at the upper end of the gas cylinder clamp lifting frame, and comprises a cylinder valve opening-closing motor; and a lifting mechanism is arranged at the top end of the rack. By adoption of the automatic gas distribution device provided by the invention, the damage to filling personnel can be avoided when danger occurs in the gas distribution process; meanwhile, the gas distribution efficiency can be greatly improved and the weighing accuracy can be guaranteed; and the proportion of each gas can be very precise.