Sulfonated poly(ether ketone)s containing 3,5-dimethyl phthalazinone moieties (SPPEK-DMs) with different degrees of sulfonation (DS) were synthesized ,via, direct polycondensation from 4-(3,5-dimethyl-4-hydroxyphenyl)-2,3-phthalazinone, 4,4′-difluorobenzophenone and 3,3′-disulfonate-4,4′-difluorobenzophenone. The chemical structure of SPPEK-DMs was characterized by FTIR and ,1,H-NMR. Thermal stability of SPPEK-DMs was characterized by the thermogravimetric analysis. The membranes prepared from SPPEK-DMs exhibited ion exchange capacities (IEC) ranging from 0.93 mmol·g,-1, to 1.86 mmol·g,-1,. Water uptake, swelling, oxidative stability and methanol permeability of SPPEKDMs membranes were investigated. SPPEK-DMs membranes exhibited high oxidative stability. The methanol permeability values of SPPEK-DMs membranes were in the range 5.15 × 10,-8,-6.61 × 10,-7, cm,2,·s,-1, which was much lower than those of Nafion117. The proton conductivity of SPPEK-DM40 membranes was 1.1 × 10,-2, S·cm,-1, at 70℃.