A series of phosphoric acid (PA) doped imidazolium poly(phenylene oxide) (PPO) membranes with different methylimidazole (MeIM) contents were prepared to tailor the performance of solidstate membranes. First, brominated poly(phenylene oxide) (BPPO) was synthesized by methyl bromination. Then BPPO was reacted with MeIM and doped with PA. The process was confirmed by Fourier transform infrared spectroscopy and C-13 NMR The PA absorption ability of the imidazolium poly(phenylene oxide) (PPO-MeIM) membranes changed with increasing MeIM content. PPO-MeIM membrane showed the best proton conductivity of 6.79 X 10(-2) S cm(-1) at 0% relative humidity, the highest mechanical strength of 4.8 MPa at the molar ratio of 4:10 (M-3#) at 30 degrees C, and high power density of 260 mW cm(-2) without additional humidification at 160 degrees C. Results indicated that incorporation of an appropriate amount of MeIM groups can achieve the best proton conduction performance and mechanical properties.