The geometrical structure of ferromagnetic FeO is optimized. Its electric and magnetic properties such as the half-metallicity, the conductivity and the magnetic moment distribution are investigated by performing first-principles calculations within the generalized gradient approximation for the exchange-correlation function based on density functional theory. Results show that ferromagnetic FeO has 100% spin-polarization at the Fermi level. Its supercell magnetic moments are 32.00 μB, which arise mainly from 3d-orbits of Fe-ions. The electronic structures of Fe-ions are Fe2+t2g3↑eg2↑t*2g1↓.