The Mg acceptors of GaN films are activated as p-type GaN with rapid thermal annealing (RTA) and furnace treatments. The GaN:Mg films are activated successfully by using the RTA system below 1000°C for 1 min. After the RTA treatment, we observed a sharper linewidth and stronger emission intensities from donor to acceptor peaks in the photoluminescence spectra. By comparing the electrical properties of GaN:Mg films at optimum conditions made with RTA (800°C) and furnace (700°C) treatments, we find similar activated hole concentration and a higher hole mobility for GaN:Mg films with RTA treatment at 800°C. A higher bulk resistivity caused by increasing nitrogen vacancies is found at higher temperature and longer time RTA treatments. Faster treatment times and lower temperatures for the GaN:Mg films were achieved with the RTA activation process.