Gallium nitride (GaN) epilayers with nanopore arrays were fabricated by inductive coupled plasma (ICP) etching using anodic aluminum oxide (AAO) as mask.Nanoporous AAO templates were formed by anodizing the Al films deposited on GaN epilayers.The diameter of the perforations in the AAO masks could be easily controlled by tuning the technique parameters of AAO fabrication process.Cl2/Ar and Cl2/He were employed as etching gas.Scanning electron microscopy (SEM) analysis shows that vertical nanoporous arrays with uniform distribution can directly be transferred from AAO masks to GaN films in some proper conditions.Photoluminescence (PL) spectra, X-ray diffraction (XRD) and Raman spectroscopy were applied to assess properties of the nanoporous GaN films with different average pore diameters and interpore distances.