The invention discloses a phosphogypsum based elevation greening wallboard and a preparation method thereof. The preparation method of the phosphogypsum based elevation greening wallboard comprises steps as follows: slurry containing 80%-90% of semi-hydrated phosphogypsum, 1%-5% of a foaming agent and 10%-15% of fibers is poured into a mold provided with geocells and is subjected to casting to be latticed, flexible reinforced materials are arranged in lattices, the slurry can be subjected to drying sintering or natural drying forming, then plant growing geocells are filled with plant culture media, and grass seeds are scattered on two sides of the plant culture media in advance or plants are grown on the two sides of the plant culture media. According to the preparation method, solid waste is adopted as a main material, waste is changed into wealth, and comprehensive utilization of the waste is realized; a product is rich in bubbles, thereby being low in density, light in weight and low in transportation cost; by means of rich fibers in the product, the tensile property of the product is good; by means of polymer yarn in the product, the bending resistance and the fracture resistance of the product are good; the phosphogypsum based elevation greening wallboard has functions of beautifying the environment and purifying air, has certain sound absorption and insulation effects, is low in manufacturing cost and has good market application prospect.