The invention discloses a preparation method of a Ni-based alloy composite board, which relates to a preparation method of an alloy composite board. The invention solves the problems that the traditional single nickel-based high-temperature alloy can not be applied to an oxidation environment of above 1000 DEG C, the single Ni-Al intermetallic compound has room temperature brittleness and poor machinability and the traditional preparation method of the composite board has a plurality of defects. The preparation method comprises the steps of: pre-grinding alloy, ultrasonically cleaning, coating AlCl3 powder or NH4Cl powder, or wiping an aluminum foil by adopting HCl, then coating by using the aluminum foil for carrying out aluminizing treatment, and then thermally treating. The Ni-based alloy composite board has small room temperature brittleness, good machinability and use temperature of 1000-1100 DEG C in an oxidation environment. The invention has the advantages of simple used equipment, easy operation, low cost, no pollution and short period. The invention can treat specific parts of the thin board to form a microcell composite board with better flatness, and avoids the formation of cavities in a bed interface.