The invention discloses a preparation method of a high-zinc magnesium alloy ingot casting and relates to the preparation method of the alloy ingot casting. The invention aims to solve the problems that the existing high-zinc magnesium alloy ingot casting is easy to generate element segregation in the casting process and due to improper selection on a cooling water pressure, a casting speed and a melt temperature, a great number of cracks are generated. The preparation method comprises the following steps: 1, weighing materials; 2, feeding the materials; 3, smelting; 4, refining and standing; 5, casting. The preparation method has the advantages that 1, the high-zinc magnesium alloy ingot casting prepared by the preparation method is uniform in tissues and has no phenomena of pore loosening and slag inclusion and a melt has low impurity content; 2, the high-zinc magnesium alloy ingot casting prepared by the preparation method has a diameter of 405 mm to 485 mm, complete appearance and no obvious cracks. The high-zinc magnesium alloy ingot casting can be obtained by the preparation method.