Abstract: Sulfonated aromatic copolymers have emerged as a promising alternative to perfluorosulfonic acid membranes. Many continuous research efforts have focused on enhancing their dimensional stability, methanol permeability and proton conductivity, which are the key properties of these type of proton exchange membrane (PEM) materials. Sulfonated poly (aryl ether ketone sulfone) (SPAEKS) containing amino group and phosphonated poly(aryl ether ketone) containing carboxyl group (P-PAEK) macromolecular crosslinker were synthesized using the direct condensation method. Subsequently, the P-PAEK/SPAEKS crosslinked composite membranes (Cr-SPAEKS-xP) were prepared by high temperature heat treatment. These series of crosslinked composite membranes show excellent thermal properties, mechanical properties, oxidation stability and appropriate water absorption. The crosslinked network structure effectively inhibits the water swelling and methanol permeability in the membrane, thereby improving the dimensional stability and methanol barrier properties of the crosslinked composite membrane. The swelling rate of Cr-SPAEKS-20P composite membrane at 80℃ is only 25.01%, and its methanol permeability is only 1.49×10⁻⁷ cm²·s⁻¹. The sulfonic acid group, phosphonic acid group and larger hydrogen bonding network in the membrane coordinate to promote the proton conduction of the composite membrane, and the proton conductivity of Cr-SPAEKS-20P membrane could reach 0.204 S·cm⁻¹ at 100℃. More importantly, at 80℃ and 50% relative humidity, the proton conductivity of Cr-SPAEKS-20P is significantly higher than that of SPAEKS membrane, which can reach 0.029 S·cm⁻¹. This indicates that this series of crosslinked composite membranes holds considerable potential for application in proton exchange membrane fuel cells.