Consider that a variable composition structure can introduce an internal field, stability, and photoelectric features of Ga1-xAlxN superlattice nanowires having adjustable composition are studied. Different Al composition intervals and ratios in GaN nanowires are considered to create various superlattice nanowires. Structure and photoelectronic features of Ga1-xAlxN superlattice nanowires having diameters of 7.4, 9.8, and 12.8 angstrom are investigated based on first principles. Increasing the content of Al atoms in the corresponding sublayers can reduce the formation energy, and can appear blue shifts in optical properties such as absorption coefficient. The continuously gradual built-in electric field makes Ga1-xAlxN superlattice nanowires have a lower work function. The lowest work function can reach 4.27 eV, and the corresponding band gap is 3.812 eV. The direct band gap of Ga1-xAlxN superlattice nanowires is influenced by the nanowire diameter, length, and sublayer. These studies can provide early guidance for improving the performance of spin-polarized electron sources.