The invention provides a preparation method for an aluminum brazing organic flux. An alumina film can be damaged at the temperature of 180 DEG C-275 DEG C, deformation is small after the alumina film is welded, stabilizing and shaping is achieved, corrosion is avoided, corrosion to aluminum and aluminum alloy is very small, the welding temperature is far from the melting point of an aluminum material, the welding process is reliable, and the brazing qualified rate is greater than 98%. According to the technical scheme, 70 wt%-90 wt% of triethanolamine, 1 wt%-5 wt% of zinc tetrafluoroborate hydrate, 5 wt%-10 wt% of cadmium fluoroborate, and 5 wt%-10 wt% of ammonium fluoroborate are added; the zinc tetrafluoroborate hydrate, the cadmium fluoroborate and the ammonium fluoroborate are weighed at the room temperature and put into a mortar to be ground into fine powder, and grinding and mixing are uniform; the uniformly ground and mixed drug is poured into the weighed triethanolamine, and after being stirred uniformly, the drug is placed for a certain period of time. The welding problems of the aluminum, the aluminum alloy, aluminum bronze and aluminum brass at the temperature of 180 DEG C-275 DEG C are solved through the preparation method.