Sulfonated poly(arylene ether phosphine oxide)s with various distributions and contents of pendant sulfonic acid groups were synthesized through direct polycondensation. The microscopic structure of their corresponding membranes was well controlled by tuning the distribution and content of sulfonic acid side groups while their polymer backbones remained unchanged. As a result, the simultaneous improvement of their proton conductivity and oxidation resistance as well as dimensional stability was realized, which was very difficult for hydrocarbon proton exchange membranes (PEMs). Meanwhile, the resulting membrane showed outstanding overall properties such as a swelling close to that of Nafion 117 and 1.6 times the proton conductivity of Nafion 117. Moreover, it showed the best oxidative stability among the hydrocarbon PEMs with approximate proton conductivity so far.