The invention discloses a nutrient soil for green garden flower cultivation and a preparation method thereof. The nutrient soil for green garden flower cultivation is prepared from the following raw materials in parts by weight: 25 to 35 parts of amino acid, 20 to 25 parts of dregs of decoctions,11 to 18 parts of vitamin B6, 6 to 11 parts of calcium nitrate terahydrate, 10 to 15 parts of humus, 8 to 15 parts of EDTA chelated zinc, 11 to 22 parts of feeding maggots, 6 to 12 parts of potassium ferrate, 8 to 11 parts of red brick clasts, 1 to 3 parts of bacillus subtilis, 3 to 5 parts of plant ashes, 4 to 9 parts of watermelon juices and 10 to 20 parts of sodium naphthalene-1-acetate. The nutritive soil has the functions of helping the garden cultivated plants to absorb the nutrient elements in various growth stages evenly, increasing the plant nutrition, promoting the plant growth, improving the plant resistance and resisting the plant disease; coordinating the humus with the plant ashes can improve the fertilizer efficiency duration, while long-term growth of flower is well maintained, light nutrient substrate raw materials of the EDTA chelated zinc, the potassium ferrate, the red brick clasts and the like are used, the transportation cost of the substrate is significantly reduced, and the nutrient soil is suitable for greening of the garden flowers due to the long-term and light characteristics.