The invention relates to a membrane separation and yeast reuse technique for matured mash of molasses alcohol. The technique is characterized by transporting the matured mash to a filter membrane (microfiltration or ultrafiltration) through a pump, separating under the sterile and seal conditions, reusing a yeast concentrated liquid for fermentation, and redistilling a penetrating fluid; and concentrating distillate, and then adding organic matters so as to form an organic fertilizer. In the technique, the pore size of a microfiltration membrane is 0.02-10mu m, the flow speed is controlled to 0.5-5m/s, the pressure is 0.01-0.2Mpa, and the temperature is 0-50 DEG C; and the pore size of the ultrafiltration membrane is 0.001-0.02 mu m, the flow speed is controlled to 0.1-0.5m/s, the pressure is 0.1-0.5Mpa, and the temperature is 0-50 DEG C. The technique has the advantages that the yeast concentrated liquid is reused so that cyclic utilization of resources is achieved, thus the technique is economic and environmentally-friendly; the filtrated penetrating fluid is redistilled, the chemical oxygen demand (COD) removal rate is larger than 50%, and the loss of the alcohol is less than 2.5%; and the distillate is concentrated so as to prepare the organic fertilizer, thereby achieving the zero emission of the waste liquid.