The invention belongs to the technical field of environment engineering and particularly relates to a method for separating and recycling heavy metal from garbage incineration fly ash and conducting hazard-free treatment on the fly ash. The method comprises the steps that after the household garbage incineration fly ash is diluted through an acidic sulphur oxidation bacteria culture medium solution, sulphur balls are added, so that acidic leach liquor containing the heavy metal is obtained; after a proper amount of alkali is added for pH adjustment, hydrogen sulfide gas is introduced into theacidic leach liquor; the hydrogen sulfide gas reacts with the heavy metal, so that sulfide precipitation is formed; and after solid-liquid separation is completed, recycling is conducted in the form of the sulfide precipitation, so that the pure heavy metal is obtained. The treatment process is implemented at the normal temperature and normal pressure; energy consumption is low; the process is simple; the large-scale engineering potential is achieved; a biological leaching energy source substance, namely sulphur, is recycled to be reused, so that the post-acidification problem of the treated fly ash is solved; the heavy metal entering the leach liquor is subjected to reduction and precipitation conducted through sulfate, so that the heavy metal is separated or recycled or removed effectively; and the sulfate and pH problems are solved at the same time.