NOVELTY - Processing prepared Rehmannia root is carried out by selecting prepared Rehmannia root medicine material, removing impurity, and grading according to size; washing medicine material in a drum-type washing machine for 3-4 hours; steaming the medicine material at normal pressure for 7-8 hours; drying the material and controlling water content to 15-18%; putting dried material into a sack and stacking to 1-2 m high; taking the material out and cutting into thick sheet; and drying the thick sheet to moisture content of not greater than 15% to obtain the finished product.    USE - Method of processing prepared Rehmannia root (claimed).    ADVANTAGE - The method has high production efficiency and high yield, is energy saving and suitable for large scale industrial production. The planting method is simple and green and low in cost, can make prepared rhizome of Rehmannia to yield high nutrient content is high, and does not cause pollution to the environment.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for planting method of prepared Rehmannia root comprising:    (A) selecting and drying seeds, soaking seeds into liquid medicine for 13-15 hours, and then taking out the seeds for sowing, where the buffer solution contains 1-2% acetic acid, 1-2% ammonium molybdate, and 2% zinc sulfate;    (B) selecting suitable soil which is loose, fertile, well-drained with water and sandy soil for planting, adding wood ash, lees, powdered rock phosphate, bentonite and ammonium hydrogen carbonate at a layer of 2-3 cm;    (C) uniformly excavating upper soil surface at depth of sowing hole of 4-6 cm, adding 4-0.6% microelement and 15-20% phosphate and then covering with soil, then uniformly spreading seeds into the soil, and sowing at 4-6 seeds for each sowing hole;    (D) keeping soil and field free from weeds, keeping daily temperature at 23-33 degrees C and nightly temperature at 3-10 degrees C and high humidity environment so as to slow seedling stage;    (E) applying every 1-2 months with fertilizer comprising 5-10 kg slow-releasing urea, 3-5 kg potassium chloride, 10-15 kg monocalcium phosphate, 2-3 kg ferrous sulfate, 0.5-1 kg borax, and 0.2-0.3 kg ammonium phosphate;    (F) preventing and treating diseases in seedlings with disease preventing agent, where disease comprises spot blight, ring spot, or blight; and    (G) harvesting in November by carefully picking stem.