Na-doped boron nitride (BN) microbelts with room-temperature ferromagnetism and electrical conductivity have been synthesized by nitriding-reduction reaction. The BN microbelts exhibit a belt-like morphology with a length of 50-200 mu m, a width of about 2 mu m and a thickness of about 0.85 mu m. The saturation magnetization is 0.05 emu g(-1) at 300 K when Na-doped content is 0.51 at.%, indicating that the Curie temperature (T-c) is higher than 300 K. Most importantly, the half metallic ferromagnetic Na-doped BN microbelt exhibits typical semiconductor electrical conductivity. This observation suggests that Na doping converted the BN microbelts from insulators to semiconductors. First-principles calculations show that magnetic properties are derived from coupling between the Na 3s orbital, N 2s, and N 2p orbitals and that electrical conductivity is attributed to the Na doping, causing the Fermi level to cross the conduction band.