[en] Under the generalized gradient approximation (GGA), the electronic and magnetic properties of the perfect and vacancy defect AlN nanoribbon with both zigzag edge (ZAlNNR) and armchair edge (AAlNNR) are studied using the first-principles projector-augmented wave (PAW) potential within the density function theory (DFT) framework. Both ZAlNNR and AAlNNR are semiconducting and nonmagnetic, and the indirect band gap of ZAlNNR and the direct band gap of AAlNNR decrease monotonically with increase in ribbon width. A single non-edge Al vacancy makes either ZAlNNR or AAlNNR a semi-metal and thus yields complete (100%) spin polarization as well as a significant magnetic moment. Hence a single non-edge Al vacancy defect AlNNR can be used to construct efficient spin-polarized transport devices. But a single non-edge N vacancy induces a small magnetic moment in AAlNNR only. The AlNNR with a single edge N or Al vacancy is still semiconducting and nonmagnetic, leading to additional states only within the gap region and thus reducing the band gap width, except for a single edge Al vacancy in AAlNNR.