Abstract Novel sulfonated poly(phthalazinone ether ketone) (SPPEK) was synthesized by direct polymerization via N C coupling reaction. The membrane based on SPPEK was simply obtained by casting from 5% solution of SPPEK in N , N -dimethylacetamide (DMAc) at 60 °C. The as-made membrane was characterized by ion-exchange capacity (IEC), thermal analysis, proton conductivity, single cell performance and electrochemical impedance spectra (EIS). The SPPEK membrane showed excellent characteristic as a proton exchange membrane (PEM) for PEMFC application, such as high ionic exchange content (IEC) of 2.04 mequiv g −1 , high water uptake of 50.6% at 100 °C, the proton conductivity of 1.06 × 10 −2 S cm −1 at 20 °C, as well as the superior anti-hydrolytic ability and mechanical strength. Moreover, the membrane exhibited higher thermal stability than Nafion 115. Cell evaluation experiment demonstrated a better performance of SPPEK than that of Nafion 115-cell. Finally, electrochemical impedance spectra (EIS) was conducted to measure the charge transfer resistance to compare the difference between SPEEK and Nafion 115.