The blend membranes based on poly(2,5benzimidazole) (ABPBI) and sulfonated poly(ether ether ketone) (SPEEK) with different sulfonation degrees (SD) have been synthesized and characterized. These blend membranes showed increased conductivities compared with the original ABPBI membrane. After being doped by H 3 PO 4 , a maximum conductivity of 1.09×10 −1 Scm −1 of ABPBI with 16% SD SPEEK membranes was achieved at 100°C, which is six times than the maximum 1.8×10 −2 Scm −1 for the ABPBI membrane at 120°C. In the case of ABPBI with 32%SD SPEEK membranes, maximum conductivity is 3.89×10 −2 Scm −1 at 120°C, double than the maximum 1.8×10 −2 Scm −1 for the ABPBI membrane at 120°C. Moreover, the ABPBI–SPEEK blend membranes exhibited higher thermal stability and acid/water uptake than the original ABPBI membrane. Compared with the original ABPBI membrane, ABPBI–SPEEK membranes may be promising electrolyte membranes for fuel cells at medium/high temperature.