Developing high temperature proton exchange membranes (HT-PEMs) with high conductivity and mechanical strength simultaneously is a considerable challenge for the HT-PEM fuel cell (HT-PEMFC). Herein, a 1-(3-aminopropyl)imidazole (APIm) functionalized low-cost poly(vinyl chloride) (PVC) membrane (PVC-APIm) with superior phosphoric acid (PA) doping content and high proton conductivity is synthesized via a gentle and facile method with no need for the chloromethylation procedure. The poly(ether ketone cardo) (PEK-C) polymer is blended with PVC-APIm to provide sufficient mechanical robustness. Interestingly, blending PEK-C not only improves the mechanical stability, but also increases the PA doping content of membranes. As a result, PA doped PVC-APIm/x%PEK-C membranes possess increased tensile strength and upgraded conductivity simultaneously. The PVC-APIm/10%PEK-C/166%PA membrane exhibits a low area swelling of 45%, high conductivity of 0.132 S cm⁻¹ at 180 °C and suitable tensile strength of 11.8 MPa at room temperature. The single cell performance of this membrane demonstrates the technical feasibility of the PVC-APIm/x%PEK-C/PA membrane for the HT-PEMFC.