A series of cardo poly(aryl ether sulfone) copolymers bearing pendent sulfonic acid groups(SPES-X) have been prepared by a facile chemical graft method. The structure was confirmed by 1H-NMR spectra. The side-chain-type SPES-X membranes show significantly reduced swelling behavior and excellent mechanical properties as well as appropriate proton conductivity compared to the main-chain-type sulfonated polymers with similar ion exchange capacity(IEC) value. Moreover, they show methanol permeability in the range of 0.6 × 10-7-5.7 × 10-7 cm2/s which is lower than that of Nafion 117. All the results indicate that the SPES-X membranes are promising candidates for the direct methanol fuel cells. A series of cardo poly (aryl ether sulfone) copolymers bearing pendent sulfonic acid groups (SPES-X) have been prepared by a facile chemical graft method. The structure was confirmed by 1H-NMR spectra. The side-chain-type SPES- membranes show significantly reduced swelling behavior and excellent mechanical properties as well as appropriate proton conductivity compared to the main-chain-type sulfonated polymers with similar ion exchange capacity (IEC) value. Moreover, they show methanol permeability in the range of 0.6 × 10- 7-5.7 × 10-7 cm2 / s which is lower than that of Nafion 117. All the results that that the SPES-X membranes are promising candidates for the direct methanol fuel cells.