The invention discloses an aluminum alloy sodium removal agent and a preparation method thereof. The aluminum alloy sodium removal agent comprises the following raw materials in parts by weight: potassium chloride, potassium fluoroaluminate, magnesium chloride, hexachloroethane, water and impurities, wherein the impurities are a mixture of ammonium chloride, ammonium carbonate and ammonium bicarbonate. The preparation method of the aluminum alloy sodium removal agent comprises the following steps: weighing all the raw materials according to the weight parts, sequentially adding the potassium chloride, magnesium chloride, hexachloroethane and potassium fluoroaluminate into a ball mill for ball milling, evenly mixing and screening, detecting and packaging. Residues can be removed by adsorbing and dissolving oxides and entrainments in a melt through a solvent, so that the aluminum slag burning phenomena can be effectively reduced, metal loss can be decreased, and further the production cost is lowered; the usage amount of the product is less, only 1-1.5kg sodium removal agent is need for removing 1kg of sodium, more than 80% of sodium in aluminum water can be removed, the potassium fluoroaluminate used is non-hydroscopic and non-toxic, the production environment is purified, smoke emission is reduced, and the aluminum alloy sodium removal agent is stable in performances.