The invention relates to a dedicated dye for superfine fiber synthetic leather and a preparation method thereof. The preparation method adopts a multi-component blending modification technology to prepare a dedicated dye for superfine fiber synthetic leather, and the dedicated dye is used for dyeing superfine fiber/polyurethane synthetic leather. The preparation method comprises the following steps: preparing the following raw materials in parts by weight: 20 to 50 parts of weak acidic dye, 30 to 70 parts of metal complex dye, 3 to 15 parts of dispersant, and 2 to 6 parts of pH adjusting agent, then mixing the raw materials mentioned above, and grinding the mixed raw materials into powder with a size more than 600 meshes by a grinder so as to obtain the target product. The dedicated dye, which is used for dyeing superfine fiber synthetic leather, can balance the coloring amount between two components of superfine fiber and polyurethane and automatically regulate the pH value required by the dyeing during the dyeing process, the dyeing process is simple, the dyeing is uniform, the wet rub fastness of the dyed superfine fiber synthetic leather can reach 3 grade or more, and the dry rub fastness of the dyed superfine fiber synthetic leather can reach 4 grade or more.