The invention relates to a plating solution for chemical zinc plating of magnesium alloy, wherein, the plating solution is an aqueous solution containing zinc salt, complexing agent and auxiliary agent; the auxiliary agent is selected from one or more sorts of copper sulphate, sodium nitrate, ferrous sulfate and iron chloride; moreover, the auxiliary agent assists the deposition of the zinc salt to improve the structure and the density of zinc plating coat and prevent the oxygen in the air from contacting magnesium alloy, thereby effectively preventing magnesium alloy corrosion. When the auxiliary agent is selected from one or more sorts of copper sulphate, ferrous sulfate and iron chloride, other metallic ion in the auxiliary agent and zinc ion can be reduced to simple metallic substance which deposits on the surface of the magnesium alloy; therefore, the color of the zinc plating coat can be adjusted to present a series of colors such as grey and black.