More than 10 kinds of perovskite oxide thin films and their heterostructures have been successfully fabricated on SrTiO3(STO) (0 0 1) substrates by laser molecular beam epitaxy (laser MBE). Measurements of atomic force microscopy (AFM) and high-rt solution transmission electron microscopy (HRTEM) reveal that the surfaces and interfaces are Atom level smooth. The unit cell layers and the lattice structure are perfect. The enhancement of secund-harmonic generation (SHG) in BaTiO3/SrTiO3 9BTO/STO) superlattices and the thickness dependent structural characteristics of BaTiO3 (BTO) thin fillns were observed. The all-prrovskite oxide P-N junctions have been successfully fabricated and better I-V curves were observed.