The effects of operating conditions on the permeate flux for ultrafiltration of aqueous solution of PVP-360 in hollow-fiber membrane modules, have been investigated based on the exponential model with the consideration of the declines of transmembrane pressure along the axial direction in the hollow fibers. It is seen that the exponential model qualitatively correlates the experiment. The correlation prediction may be improved if the exact but complicated pressure distribution is used for the derivation of presented model.