The permeation characteristics of water, methanol, benzene and heptane through six kinds of porous glass membranes with pore diameters of 4, 12, 50, 70, 100, 200nm were studied. For 4nm membranes, the liquid flow was different from Poiseuille flow and was affected by the pore wall. Further, the porous glass membranes were modified with trimethylchlorosilane (TMS) and propane sultone (PS). For 4nm membrane, high fluxes of hydrophobic and hydrophilic liquids were obtained for hydrophobic and hydrophilic surfaces, respectively. For example, the flux of liquid through the porous glass membrane modified with TMS was, in the decreasing order, heptane>benzene>methanol=water. This order corresponded with the results of measurement of contact angle.