Sulfonated poly(styrene-ethylene-buthylene-styrene) (SSEBS) for a polymer electrolyte membrane was prepared according to the capacity of ion exchange. SSEBS was sufficient to utilize with the polymer electrolyte membrane from the viewpoint of appearance, tensile strength, and ionic conductivity. The SSEBS/SiO2/Plasticizer composite polymer electrolyte for the polymer battery was fabricated with various silica contents. LiClO4 or LiCF3SO3 was used as a salt, EC/PC (1: 1 vol.%) as solvents, SiO2 as a filler, and DBP as a plasticizer, respectively. The ionic conductivity was enhanced with increasing the degree of sulfonation. The ionic conductivity reached 2.6 X 10(-3) S/cm when the content of silica was 12 wt.% at 1 M LiClO4 in EC/PC (1:1 vol.%) and 40 wt.% for plasticizers. However, if the content of silica was too excessive, the ionic conductivity was decreased due to restriction of ionic movement. (C) 2003 Elsevier B.V. All rights reserved.