The invention relates to a fly ash melting tail gas purification technology which comprises the following steps: fly ash melting furnace tail gas passes through a quenching device firstly to be cooled to 100 DEG C or below and then enters a crystal nucleus agglomeration chamber, heavy metal chlorides in the tail gas form large-particle-size particulate matters and precipitate out under the action of low-frequency sound wave, the large-particle-size particulate matters are separated out by a two-phase separation device, the tail gas subjected to heavy metal chloride removal continuously passes through a graphite falling film absorption tower to remove HCl gas and then passes through an acid gas scrubbing tower to remove acid gas, and finally, clean tail gas is obtained to be exhausted to the external. The purification technology provided by the invention can fully and effectively remove heavy metal chloride salts and the acid gas, prevent the phenomenon of secondary pollution caused by heavy metal salts and greatly lower the waste water treatment cost of the traditional fly ash treatment technology; and in addition, the heavy metal salts obtained by recovery is equivalent to a special heavy metal rich ore and can be used as a metallurgical raw material.