Polycrystalline Al film has been widely used in electronics and plasmonics, but the high density of grain boundaries causes conductivity deterioration, electromigration failure or incompatibility with fabrication of complex nano-circuits. In this letter, we propose an alternative approach to overcome the problems encountered with the use of polycrystalline Al film. Single-grain crystal of Al has been grown selectively in Al thin film by micron chevron-shaped laser beam scanning. The single-grain crystal, which is free of grain boundary, is of about 9-mu m width and its length is comparable with the laser scan distance. A detailed investigation shows that the width of the single-grain crystal depends mainly on the laser power, whereas the crystal orientation depends on both the laser power and scan pattern. A wide-area of single-grain stripes can also be realized by a two-dimensional scan. The approach could be applicable to other metallic films, which are widely used in microelectronic and plasmonic devices.