Cast DNA/polyethyleneimine (PEI) blend membranes containing different amounts of DNA were prepared using acid-base interaction and characterized with the aim of understanding the polymer electrolyte membrane properties. Two different molecular weights of PEI were used to provide the mechanical strength, while DNA, a polyelectrolyte, was used for the proton transport channel. Proton conductivity was observed for the DNA/PEI membrane and reached approximately $3.0{ imes}10^{-3}S/cm$ for a DNA loading of 16 wt% at $80^{circ}C$. The proton transport phenomena of the DNA/PEI complexes were investigated in terms of the complexation energy using the density functional theory method. In the case of DNA/PEI, a cisoid-type complex was more favorable for both the formation of the complex and the dissociation of hydrogen from the phosphate. Since the main requirement for proton transport in the polymer matrix is to dissociate the hydrogen from its ionic sites, this suggests the significant role played by the basicity of the matrix.