NOVELTY - The method comprises slowly adding soda to the mycophenolic acid fermentation liquid while stirring the liquid, regulating the pH value to 8-9.5 of the fermentation liquid, continuously stirring the liquid for 30-60 minutes, and filtering the mycophenolate sodium liquid by a plate frame or a micro-porous ceramic membrane at an operation pressure of 0.2-0.3 Mpa to obtain clarified liquid at an operation temperature of less than 40 degrees C and a pressure of 5.0-6.0 bar and then performing ultrafiltration at an operation pressure of 3.0-6.0 bar to remove protein and polysaccharide.    USE - The method is useful for preparing mycophenolate sodium from mycophenolic acid fermentation liquid.    ADVANTAGE - The method is capable of simply, rapidly and economically preparing the mycophenolate sodium with high quality and reduced energy consumption in an environmentally friendly manner.    DETAILED DESCRIPTION - The method comprises slowly adding soda to the mycophenolic acid fermentation liquid while stirring the liquid, regulating the pH value to 8-9.5 of the fermentation liquid, continuously stirring the liquid for 30-60 minutes, filtering the mycophenolate sodium liquid by a plate frame or a micro-porous ceramic membrane at an operation pressure of 0.2-0.3 Mpa to obtain clarified liquid at an operation temperature of less than 40 degrees C and a pressure of 5.0-6.0 bar and then performing ultrafiltration at an operation pressure of 3.0-6.0 bar to remove protein, polysaccharide, color forming substances and other macromolecular impurities of the clarified liquid, desalting and concentrating the ultrafiltrate for 3-5 times by a nanofiltration membrane, where the volume of the concentrated solution is 20-30% of that of the ultrafiltrate, and concentrating and drying the collected liquid of the nano-filtration membrane in vacuum to obtain the mycophenolate sodium powder. The membrane flux of the ceramic membrane is 35-45 L/h.sq.m2 with an aperture of 0.05-0.15 microns. The ultra-filtration membrane in the step of performing the ultrafiltration has the molecular weight cutoff of 6000-8000 and the membrane flux of 40-45 L/h.sq.m2. The operation temperature of the nano-filtration membrane liquid is 25-30 degrees C. The operation pressure of the ultra-filtration membrane in the desalting and concentrating step is 8.0-12.0 bar with the molecular weight cutoff of the membrane of 600-800 and the membrane flux of 30-35 L/h.sq.m2.