The invention provides a cored wire for preparing a nickel-based high-aluminum coating and a coating preparation method of the cored wire, and belongs to the field of thermal spraying in material processing engineering. The cored wire comprises the following components in percentages by mass: 13-25% of Cr, 4-10% of Al, 3-6% of B, 3-6% of Si, and the balance Ni and inevitable impurities. A strip for the skin of the cored wire is a Ni80-Cr20 strip. When the nickel-based high-aluminum coating with good high-temperature corrosion resistance is prepared by electric arc spraying, conditions of a spraying process are as follows: current is 160-200 A, voltage is 28-34 V, pressure of compressed air is 0.4-0.6 MPa, and spraying distance is 190-210 mm. By the cored wire and the coating preparation method, the nickel-based high-aluminum coating with high hardness and good high-temperature corrosion resistance can be obtained.