Poly(phenylene ether) (PPO) was chosen as raw material because of its high strength and good processing properties, to prepare the high temperature Bronsted acid-base polymer membrane. PPO was first bromomethylated by free radical reaction, then reacted with different contents of methylimidazole (Im), finally doping phosphoric acid (PA) to prepare BPPO-Im/PA membrane. The proton exchange membranes were characterized by ¹³C-NMR and FT-IR. The bromination degree is 15.33%, 28.66% and 36.07%, respectively. The amount of Im increases with increase of the bromination degree and the PA uptake increases from 40% to 380%. The thermal stability of the BPPO-Im membranes is proved with increase of Im. The conductivity increases first and then decreases with increase of the PA uptake, and the mechanical properties decrease gradually. The B2-Im/PA membrane with the bromination degree of 28.66% exhibits the best comprehensive properties. The B2-Im/PA membrane has good thermal stability below 200 ℃ detected by TG and good tensile strength of 5.2 MPa. A high conductivity of 0.054 S/cm is achieved at 160 ℃ for the membrane.