The invention relates to an alkaline electroplating Zn-Ni alloy additive, an electroplating solution and a preparation method. The additive comprises the following components in parts by weight: 3.5 to 4.5 parts of nickel complex agent, 6 to 8 parts of nickel source, 7 to 8.5 parts of zinc complex agent, 1.5 to 2.5 parts of brightening agent and 0.2 to 0.3 part of throwing agent. The preparation method comprises the following steps: adding zinc oxide into dissolved sodium hydroxide, stirring and dissolving; adding the zinc complex agent, the nickel complex agent, nickel replenisher, the brightening agent and the throwing agent in turn; and stirring to ensure that the mixture is mixed uniformly so as to prepare the electroplating solution containing the additive. The alkaline electroplating Zn-Ni alloy additive can acquire excellent metal distribution and constant alloy composition within a wide current density range, has stable nickel content of the plating in a range of between 12 and 15 percent, excellent corrosion resistance which is over five times more than a conventional zinc coating, excellent dispersive power and higher current efficiency, and can be used for barrel plating or rack plating with small coating stress, high ductility and excellent brightness.