Atomic-scale epitaxial BaTiO3 (BTO) thin films were grown on SrTiO3 (STO) substrate by computer-controlled laser molecular beam epitaxial system. The crystal quality, surface and interface microstructure of the laser MBE BTO thin film has been investigated by in-situ reflection high- energy electron diffraction, x-ray diffraction, transmission electron microscope and atomic force microscope. We find that the laser MBE BTO thin film prepared at ozone pressure of 10-6 Torr and at STO substrate temperature of 750 degrees C has highly c-axis oriented tetragonal phase and single crystal structure, the BTO/STO interface is abrupt, and the surface of the BTO thin film shows atomically smooth.