NOVELTY - Three-stage biologically purification and treatment of wastewater from sugar factory includes flowing the wastewater at sugar factory in the cooling circulation pool; adding composite bacterial flora propagation expanding liquid including methanobacterium and anaerobic heterotrophic bacteria; processing the wastewater in the anaerobic biologic pool; adding composite bacterial flora propagation expanding liquid; and standing the anaerobically biologically processed wastewater in the water culture plant pool; and planting the Smilacina atropurpurea in the expanding liquid.    USE - Method for three-stage biologically purification and treatment of wastewater from sugar factory (claimed).    ADVANTAGE - The purified drain water can be recycled, completely; the water is saved at more than 70%; and the removing rates of ammonia nitrogen, total nitrogen and total phosphorus are more than 70-80%.    DETAILED DESCRIPTION - Three-stage biologically purification and treatment of wastewater from sugar factory comprises: (A) flowing the wastewater at sugar factory in the cooling circulation pool; when the water is at less than 50 degrees C, entering in the anaerobic biologic pool and processing at the first stage; adding composite bacterial flora propagation expanding liquid including methanobacterium and anaerobic heterotrophic bacteria comprising hydrogen-producing bacillus of 101% of the pool water volume and standing for 6-8 hours; (B) processing the anaerobically biologically processed wastewater in the anaerobic biologic pool including a multi-stage oxidation pool and the reinforced micropore aeration pool at the second stage; adding composite bacterial flora propagation expanding liquid including Rhodospirillum rubrum and Bacillus mucilaginosus of 101% of the pool water volume and standing for 3-5 hours; and immersing the composite filler with perfect bacterial liquid absorbing performance in the anaerobic biologic pool; and (C) standing the anaerobically biologically processed wastewater in the water culture plant pool for 5 hours; planting the Smilacina atropurpurea in the composite bacterial flora propagation expanding liquid floated on the water surface of the plant pool, where the composite bacterial flora propagation expanding liquid includes Rhodospirillum rubrum and Bacillus mucilaginosus.