A novel polyacrylonitrile (PAN)/phosphotungstic acid (PWA) doped PVDF composite membrane was successfully prepared by blending electrospinning. Impedance spectroscopy and scanning electron microscopy characterization showed that the electrospun composite membranes possess comparatively higher proton conductivity and well-defined microstructure. In particular, the addition of hydrophilic PAN can effectively improve the water uptake performance of composite membrane and simultaneously no obvious membrane swelling was found. The experimental results showed that excellent composite membranes can be obtained by 30% PAN doping, and more than 30% PAN doping will increase the diameter of composite nanofiber membrane and accelerate the loss of PWA. The production of high-quality composite membranes with optimized PAN and PWA compositions can be achieved, which are promising candidates for proton exchange electrolyte membranes.