The invention provides an amphoteric ionic warm asphalt mixing agent and a preparation method thereof. A molecule of the amphoteric ionic warm asphalt mixing agent contains three quaternary ammonium salt ions; the preparation method of the amphoteric ionic warm asphalt mixing agent is as follows: firstly preparing a double-quaternary ammonium salt type asphalt emulsifier, then, mixing epoxy chloropropane and an inorganic acid salt with a solvent to form a reaction system to prepare an intermediate, and finally, mixing the double-quaternary ammonium salt type asphalt emulsifier with the intermediate to prepare the amphoteric ionic warm asphalt mixing agent provided by the invention, the amphoteric ionic warm asphalt mixing agent provided by the invention greatly reduces the temperature of a hot mix asphalt mixture; and meanwhile, the defect of poor water damage resistance of the asphalt mixture caused by adoption of the warm asphalt mixing agent is solved, and particularly the defect of poor blocking property on a mixture of alkaline aggregate and asphalt is solved.