The invention relates to a plant seedling solid culture medium and a preparation method thereof, in particular to a cultivation medium for cultivating grape large seedling and a preparation method thereof. The technical problems that for an existing cultivation medium for cultivating the grape large seedling, content of hazardous substances is high, regular growth of plants is unfavourable, nutrient substances are imbalanced, and the production cost is high are mainly solved. The cultivation medium for cultivating the grape large seedling is prepared by overrotten corn straw powder, garden soil, perlite, particle slow release fertilizer, trace-element fertilizer, fungicide and water. The cultivation medium for cultivating the grape large seedling and the preparation method thereof have the advantages that the content of the hazardous substances is low, the regular growth of the plants is facilitated, the nutrient substances are balanced, and the production cost is low.