Remanence properties and magntization reversal mechanism of Fe nanowire arrays with diameters 16nm and 130 nm are studies. Isothermal remanent magnetization curves show that the contribution of irreversible magnetization decreases when the diameter changes from 16nm to 130nm. The remanence coercivities of these nanowires obtained in dc-demagnetization curve are about 2400 Oe and 800 Oe, respectively. The magnetization reversal mechanism is different in these two samples. For the nanowire array with diameter 16nm, both the mucleation and the pinning have effects on magnetization reversal mechanism, and the pinning field (about 2500 Oe) is larger than the mucleation field (about 2200 Oe). However, for the nanowire array with diameter 130nm, the magnetization reversal mechanism is dominated by the pinning effect of domain walls.