Two series of sulfonated poly(arylene ether ketone)s (SPAEK) copolymers with sulfonic group (-SO3H), and 10% and 30% carboxylic acid group (-COOH) were prepared by post-sulfonated method, which were named SPAEK-COOH-10 and SPAEK-COOH-30, respectively. After incorporated with different ratio of nanocellulose (NCC) via solution blending method, nanocomposites were obtained and evaluated as proton exchange membranes. High proton conductivity was achieved by introducing appropriate NCC content. The conductivity of SPAEK-COOH10/NCC5 (5% NCC) reached 0.272 S cm(-1) at 80 degrees C, which was higher than that of SPAEK-COOH-30/NCC5 (0.239 S cm(-1) at 100 degrees C). The mechanical properties of SPAEK-COOH-30 series were better than that of SPAEK-COOH-10 series because of their moderate water absorption ratio, and were further enhanced with NCC insertion. SPAEK-COOH-30/NCC5 showed a tensile strength of 47.1 MPa and an elongation at break of 88.5%, an increase of 62% and 155% compared to pure SPAEK-COOH-30, respectively. Meanwhile, the formation of hydrogen-bond network between NCC and SPAEK-COOH could also much improve the dimensional stability of nanocomposite membranes compared with that of the pristine membrane. Thus, the NCC reinforced SPAEK-COOH nanocomposite proton exchange membranes was proved to be promising for the application in fuel cells.