The Al-doped ZnO (AZO) films were deposited on a glass substrate by RF magnetron sputtering in pure Ar and $Ar+H_2$ gas ambient at temperature of $100^{circ}C$ and annealed in hydrogen ambient at the temperature range from 100 to 300 $^{circ}C$, respectively. It was found that either the addition of hydrogen to the sputtering gas or the annealing treatment effectively reduced the resistivity of the AZO films. When the AZO films were annealed at the temperature of 300 $^{circ}C$ for lhr in a hydrogen atmosphere, the resistivity decreased from $2.60{ imes}10^{-3};{Omega}cm$ to $8.42{ imes}l0^{-4};{Omega}cm$ for the film deposited in pure Ar gas ambient. Under the same annealing conditions of temperature and hydrogen ambient, the resistivity of AZO films deposited in the $Ar+H_2$ gas mixture decreased from $8.22{ imes}l0^{-4};{Omega}cm$ to $4.25{ imes}l0^{-4};{Omega}cm$. The lowest resistivity of $4.25{ imes}l0^{-4};{Omega}cm$ was obtained by adding hydrogen gas to the deposition and annealing process. X-ray diffraction (XRD) pattern of all films showed preferable growth orientation of (002) plane. The average transmittance is above 85 % and in the range of 400-1000 nm for all films.