The present invention provides a zinc alloy with improved alloy characteristics such as fluidity, castability, mechanical properties, corrosion resistance and elongation, and a preparation method therefor. The method for preparing the zinc alloy, according to one aspect of the present invention, comprising the steps of: providing zinc and a magnesium master alloy including a calcium-based compound; and forming a molten metal in which the magnesium master alloy and the zinc are melted; and casting the molten metal. The zinc alloy, according to another aspect of the present invention, includes a zinc base and the calcium-based compound present in the zinc base, wherein magnesium is applied to the zinc base.