A method for purifying Al—Ti—B) alloy melt includes putting and melting industrial aluminum ingot in an electromagnetic induction smelting furnace, the melt of Al being covered by a high-temperature covering agent, and its temperature up to at about 670˜900° C.; adding material of K2TiF6 and KBF4 into the smelting furnace and then stirring the compounds therein to react; adding compound comprising Mg, L, Na and F to the evenly stirred K2TiF6 and KBF4, the compound having an amount about 0.01%˜1% of a sum weight of total K2TiF6 and KBF4, and uniformly stirring for about 15˜60 minutes under a reaction temperature being constantly at about 670˜900° C., the dregs being removed, the Al alloy being casting molded.