The invention discloses a kaolin modified mouldproof paper board and a preparation method thereof. The preparation method comprises the following steps: 1) putting Chinese herbal medicines into water to be decocted, so as to obtain a Chinese herbal medicine extracting solution; 2) in presence of ultraviolet ray, carrying out activating treatment on kaolin, plant ash, sodium chloroplatinate and molybdenum disulfide, so as to obtain an activator; 3) under acidic condition, mixing the activator with amino acid, and then modifying, so as to obtain a modified activator; 4) carrying out contact reaction on acrylic emulsion, polystyrene, dioctyl phthalate, aluminium oxide, boron nitride and sodium nitrite, then adding an emulsifying agent, the modified activator and the Chinese herbal medicine extracting solution, and mixing, so as to obtain mouldproof paint; and 5) coating the mouldproof paint on the surface of a paper board body, and drying, so that the kaolin modified mouldproof paper board is obtained. The mouldproof paper board has excellent mechanical, waterproof and antibacterial properties.