Epitaxial double-perovskite Sr2FeMoO6 films have been grown by pulsed laser deposition (PLD) on SrTiO3 substrates. High-quality metallic Sr2FeMoO6 thin films with low resistivity were obtained by deposited in a mixture gas of hydrogen and argon. Resistivity versus temperature measurements, magnetic measurement, and x-ray diffraction indicate that using a mixture forming gas of hydrogen and argon in PLD is a flexible method for preparing high-quality epitaxial Sr2FeMoO6 films. In (011) cross-section high-resolution transmission electron microscopy images of epitaxial Sr2FeMoO6 films, the clear superlattice structure of ordered cations of Fe and Mo is shown.