The invention discloses a technology for preparing a zinc-aluminum-magnesium alloy co-permeation layer based on a single-plating method. The technology is characterized in that on the basis that the technology for preparing the zinc-aluminum-magnesium alloy co-permeation layer based on the single-plating hot dipping is adopted, by means of aluminum and magnesium alloy of a certain proportion, under the condition of a certain temperature range and a certain surface processing technology, a special surface permeation assisting agent developed voluntarily is matched, and therefore the zinc-aluminum-magnesium alloy co-permeation layer is prepared on the surface of a metal material within the narrow time range (the longest time is not longer than 5 min) and the short time. According to the zinc-aluminum-magnesium co-permeation technology, the single-time permeation is provided, the technology time is short, the aluminum and magnesium content is high, and the zinc-aluminum-magnesium alloy co-permeation layer is formed. The thickness is large, the permeation layer is good in appearance, the combining strength is high, and the zinc-aluminum-magnesium alloy co-permeation layer is prepared on the surface of the metal material. The preparing method is low in cost, and industrial production and preparation are easily achieved. The zinc-aluminum-magnesium alloy co-permeation layer comprises, by weight percentage, 45%-50% of Al, 6%-12% of Mg, 34%-58% of Zn and the balance metal base material.