The invention provides a large-capacity small-size high-gradient alternating current zinc oxide resistor sheet and a preparation process thereof; the product is prepared by, with a zinc oxide powder as a main material, properly adding antimonous oxide, bismuth trioxide, cobaltic oxide, cobaltosic oxide, silicon dioxide, manganese dioxide, chromic oxide and other metal oxides, and carrying out weighing, ball-milling mixing, drying, granulation, dry pressing molding, pre-sintering, high temperature sintering, sheet grinding, heat treatment, electrode spraying, glaze coating and other processes. The product has the advantages of large capacity, small size, high electric potential gradient, safety and reliability and the like, and is suitable for use of small-sized large-capacity lightning arresters; and the preparation process is simple and convenient, and is suitable for industrialized production.