Anodic aluminum oxide (AAO) was used as a template to prepare highly ordered FeCo alloy nanowire arrays. The as-deposited samples were annealed at 300. 400, 450, 500, 550 and 600 degreesC, respectively. The structure and magnetic properties of FeCo nanowire arrays dependence on different annealing temperature were analyzed by XRD and vibrating sample magnetometer. We found that the annealing samples had large coercivity (as high as 2800 Oe) and high squareness (M-r/M-s) (about 0.9). the value of which was much larger than that of as-deposited samples (coercivity about 1500 Oe, squareness about 0.7). The temperature dependence of coercivity field H-c and squareness of the FeCo nanowire arrays associated with the microstructure has been investigated and correlated with microstructure features. such as stress relaxation. structure ordering, second phase, and grain size. (C) 2002 Elsevier Science B.V. All rights reserved.