The invention discloses a preparation method of an evaporation mask plate. The preparation method comprises the following steps: filming a core mold; exposing; developing; performing primary electroforming; performing post-treatment 1; performing secondary electroforming; performing post-treatment 2, and is characterized in that the electroforming layer thickness of the primary electroforming is equal to the thickness of a film in the step of filming the core mold; the electroforming layer of the secondary electroforming step is formed on the basis of the electroforming layer of the primary electroforming step and an exposure film formed in the exposure step. According to the evaporation mask plate manufactured by using the method, on the section of the central axes of evaporation holes, the edge lines of the evaporation holes are expanded flaring-shaped; the hole walls of the evaporation holes and the plate face of the mask plate body form an included angle of 30-60 degrees; the shelter of the hole walls of the evaporation holes to an evaporation material can be reduced, no evaporation dead angles exist during the evaporation, and the thickness of the evaporation layer is uniform; when the mask plate of the small-size evaporation holes is manufactured, the size of the evaporation holes can be smaller to improve the resolution of a display.