The invention belongs to the technical field of surface treatment electroplating, and particularly relates to a method for preparing a nickel-boron alloy coating on a continuous casting crystallizer copper plate surface. The method comprises the following step: carrying out nickel-boron alloy electroplating on a pretreated copper plate substrate, wherein the electroplating solution is composed of 30-80 g/L nickel sulfamate, 30-50 g/L boric acid, 0.8-16 g/L sodium borohydride, 30-60 g/L ethylenediamine and 0.01-0.1 g/L sodium dodecylsulfate; and the electroplating conditions are as follows: the pH value of the electroplating solution is 3.5-4.5, the temperature is 45-65 DEG C, the copper plate substrate is the cathode, nickel pellets are the anode, and the current density is controlled at 1-3 A/dm<2>. The method can be used for obtaining the coating which has the advantages of high compactness and uniformly, excellent binding force, low thermal crack tendency, high hardness, excellent corrosion resistance and excellent wear resistance.