Aluminum-doped zinc oxide (AZO) films were prepared on glass substrates using radio frequency (RF) magnetron sputtering technique. The sputtering power ranged from 25 to 100 W. Effects of the sputtering power on optical properties, crystal structure, electrical properties and infrared reflection of the AZO films were systematically investigated by UV-VIS-NIR spectrophotometry, XRD, SEM, XPS, Hall measurement and FTIR, respectively. The results reveal that the grain size is not the only parameter in determining the electrical properties of AZO films, but O-II/(O-I + O-II + O-III) ratio and Al composition are very important. The AZO films deposited at P = 75 W exhibits the lowest electrical resistivity, highest mobility and carrier concentration. The film also has the lowest packing density as well as the highest average visible transmission with a value of 84.9%. The average infrared reflection of 52% makes it a hopeful candidate for low-emissivity applications.