We fabricated the nanofiber composite membranes by impregnating Nafion into the modified polyvinylidene fluoride(PVDF) electrospinning nanofiber mat for proton exchange membrane fuel cells applications. The hydrophobic PVDF nanofibers mat became to the hydrophilic state by alkali treatment for the full embedding of Nafion into the PVDF network. The fabricated composite membranes exhibit significantly enhanced thermal stabilities, swelling resistance, and observably improved mechanical property compared to the pristine Nafion membrane. When the content of PVDF nanofiber mat is 15.1wt% in the membrane, the proton conductivity of the nanofiber composite membrane is nearly equal to that of pristine Nafion membrane with the same condition. The experimental results show that the prepared composite membrane can be used as a promising polyelectrolyte membrane for fuel cell applications.