A wurtzite N-doped MgZnO film with 20 at. % Mg (MgZnO:N) was grown by plasma-assisted molecular beam epitaxy on c-plane sapphire using radical NO as oxygen source and nitrogen dopant. The as-grown MgZnO:N film behaves n-type conduction at room temperature, but transforms into p-type conduction after annealed for 1 h at 600°C in an O flow. The p-type MgZnO:N has a hole concentration of 6.1 × 10 cm and a mobility of 6.42 cm/V s. X-ray photoelectron spectroscopy measurement indicates that substitution of N for O site is in forms of N atom (N) and N molecule (N) for the as-grown MgZnO:N, but almost only in a form of (N) for the annealed MgZnO:N. The mechanism of the conduction-type transition induced by annealing is discussed in the present work. © 2006 American Institute of Physics.