The invention discloses a linked opening/closing mechanism for a lateral carriage door of a fire truck, which belongs to the technical field of fire-fighting facility. The fire truck comprises a carriage body, an upper carriage door, a lower carriage door and an equipment frame upright; the linked opening/closing mechanism for the lateral carriage door comprises a traction wheel, an upper pulley,a lower pulley, a traction rope, a sliding device, an upper brace rod and a lower brace rod; the traction wheel is arranged on a traction wheel seat which is fixed on the inner side of the lower carriage door; the upper pulley is arranged in an upright cavity; the lower pulley is arranged on the lower part of the upright cavity; one end of the traction rope is fixed on the traction wheel, and theother end is fixed with the sliding device; the sliding device is located in the upright cavity; one end of the upper brace rod is arranged on the equipment frame upright, and the other end is hingedwith one end of the lower brace rod; the other end of the lower brace rod is connected to the sliding device; and a roller is arranged at one end of the lower brace rod hinged with the upper brace rod and is matched with the upper carriage door. The linked opening/closing mechanism has the advantages that: the upper and lower carriage doors can be opened at the same time by one operation; the open carriage doors do not interfere with the fire fighters in fetching the equipment; the opening amplitude of the upper and lower carriage doors is large; and the stability is high.