The invention discloses a sub-micron grain superplastic zinc alloy as well as a preparation method and application thereof. The sub-micron grain superplastic zinc alloy is prepared from the followingcomponents in parts by weight: more than 0 percent by weight and less than or equal to 5 percent by weight of Mn, and more than or equal to 95 percent by weight and less than 100 percent by weight ofZn, wherein the grain size of the sub-micron grain superplastic zinc alloy is at a sub-micron level. The preparation method of the sub-micron grain superplastic zinc alloy comprises the following steps: mixing and melting pure zinc and pure manganese to obtain an as-cast zinc manganese alloy; performing thermal extrusion on the prepared as-cast zinc manganese alloy for a plurality of times in order to make the accumulated deformation amount of the as-cast zinc more than or equal to 90 percent to obtain the sub-micron grain superplastic zinc alloy. Compared with the prior art, the sub-micron grain superplastic zinc alloy has the advantages of superior plasticity and toughness, and elongation rate reaches 150 to 450 percent; the preparation method is simple, and is convenient to operate, andthe sub-micron grain superplastic zinc alloy can be prepared into sub-micron grain superplastic zinc alloy fibers through further pulling treatment, so that the application range of the zinc alloy isexpanded.