The invention discloses a preparation method for a crystallizer copper plate coated with a nickel-cobalt alloy layer. The crystallizer copper plate is composed of, by mass, 1%-2% of Ni, 0.05%-0.2% of Be, 0.5%-0.7% of Al, 3.0%-5.0% of Zr, 1.2%-1.4% of Mn, 1%-3% of Mg, 0.8%-1.2% of Cr, 14.0%-16.0% of Zn and the balance Cu. The preparation method comprises the steps that a crystallizer is prepared from copper alloy comprising the components, and a coated layer is electroplated on the surface of the crystallizer. A plating solution adopted by electroplating is composed of 220-240 g/l of nickel sulfate, 17-19 g/l of nickel chloride, 5.5-6.5 g/l of cobalt sulfate, 23-27 g/l of boric acid, 5-7 g/l of potassium sulfate, 30-40 g/l of sodium chloride, 0.2-0.4 g/l of lauryl sodium sulfate and 20-22 ml/L of an additive, and the additive is a solution prepared by adding 10-12 g of sodium gluconate, 33-37 g of ascorbic acid and 22-26 g of dextrin into one liter of water. The conditions for an electroplating process are as follows, the PH value is 2.3-3.5, the electric current density is 4-5 A/dm<2>, the temperature is 44 DEG C-46 DEG C, and electroplating is conducted till the plating layer thickness reaches 1.3-1.5 mm.