Electro-microfiltration of culture broth was studied to control the selective permeation of protein solute. A flat microfiltration membrane was sandwiched between two platinum electrode plates, between which a direct current was applied. Both model suspensions, including bovine serum albumin (BSA) in baker＇s yeast suspension and real culture broth producing lytic enzyme, were filtrated in cross-flow mode. The influences of the suspension pH and the intensity of the electric field on selective permeation of protein solute were studied. When the electrode on the permeate side was used as a cathode, BSA was concentrated to the permeate solution because the BSA molecules was charged positively at pH 3.5. Meanwhile, the BSA was rejected at pH 7 because of the electric repulsion force between the molecule and the electrode of permeates side. The effects of electric field on the BSA. permeability increased with the lower permeate flux, and the higher intensity of electric current. The electro-microfiltration of real culture broth also has similar properties in the filtration of the model suspension. It was clearly found that a selective permeation of protein solutes could be controlled by changing suspension pH.