Using sulfonated polysulfone for raw material and complex additive.Adopting the method of the posture transform to preparation sulfonated polysulfone modified ultrafiltration memebrane.It’s aperture is 400-500?.Structure and separate capability have been investigated.Result show that the sulfonated polysulfone modified ultrafiltration membrane can separate solubility protein in the ferment solution of the erythromycin.Problem of the emulsification in the extraction process of the erythromycin have been resolved.