Novel sulfonated poly(arylene ether sulfone)s multi-block copolymer membranes containing highly sulfonated hydrophilic blocks were synthesized. Different local concentration of sulfonic acid in their hydrophilic blocks affected chemical and physical properties of the SPAES. To investigate the effects of chemical composition on their membrane properties, different hydrophilic oligomers sharing same hydrophobic blocks gave us exact comparison of effect of hydrophilic blocks. The higher concentration of sulfonic acid groups resulted in higher proton conductivity under certain relative humidity conditions than that of the state-of-the-art perfluorinated sulfonic acid membrane and showed that the well-developed phase separation of SPAES.