Different fluoride salts have different effects in electrolytic aluminum plants and smelters. Generally, they all reduce the primary crystallization temperature of electrolyte solution and improve the composition of electrolyte solution. For example, magnesium fluoride and aluminum fluoride can separate carbon slag and improve the conductivity of electrolyte solution. When the molecular structure is relatively high, aluminum fluoride can be adjusted in many ways. When the molecular structure ratio is low, it can be adjusted by adding sodium fluoride or ammonium bicarbonate. Adding method of aluminum fluoride: aluminum fluoride should be added in the middle of the aluminum oxide surface shell, that is, after production and processing, put a layer of aluminum oxide first, evenly sprinkle aluminum fluoride on the thin shell, and then add heat insulation materials. During the next production and processing