First, anodic aluminum oxide (AAO) membranes with a 150 nm diameter and a 230 nm interpore distance and superparamagnetism γ-Fe2O3 nanoparticles with 8 nm average diameter were prepared using hard anodization process and coprecipitation method, respectively. Then, the anionic γ-Fe2O3 nanoparticles by polyacrylic acid modification and cationic polymers were co-assembled into γ-Fe2O3 nanowire arrays in the pores of AAO membranes through a bottom-up assembly process. At last, the morphology of γ-Fe2O3 nanowire arrays was characterized by SEM. The remanence and coercivity of the nanowire arrays were nearly zero by means of a vibrating sample magnetometer (VSM), which showed that the γ-Fe2O3 nanowire arrays inherited the superparamagnetism behavior of single nanoparticles.