The heteroepitaxy in DyMnO3/ErtBa2Cu3OT_s bilayer thin films on LaAIO3 (100) substrates was characterized by four-circle X-ray diffractometry. The ErtBa2Cu3OT_6 thin films on LaAIO3 (100) substrates were prepared by molecular-beam deposition (MBD) and post-growth annealing in wet and dry 02 at 880"C, whereas the DyMnO3 thin films on the ErlBa2Cu3OT_JLaAlO3 (100) heterostructure were deposited by MBD and post-growth annealing in dry 02 at 750"C. The conventional X-ray diffraction (XRD) patterns as well as pole figures (C-scans) for specific (hid) reflections were acquired. The Err Ba2Cu3OT_6 thin film in the DyMnO3/Er~Ba2Cu307_6/LaAIOs (100) heterostructure showed [001] oriented epitaxial growth, as expected. The DyMnO3 thin film on the Er~Ba2CusO7_a epilayer in the heterostructure grew with (110) epitaxy in its metastable orthorhombic phase (lattice constants: ao= 5.272 A,, bo= 5.795 A and Co= 7.38 A). The heteroepitaxial relationships at the orthorhombic-DyMnO3 ( 110)/EriBa2Cu3OT_6 (001) interface was determined as the following: DyMnO3 (110)l[ErtBa2Cu3Ov_6 (001), DyMnO3 [ 1 i0]llEriBa2Cu3OT_6 [ 100] or Er~Ba2Cu3OT_6 [010], and DyMnO3 [001 ] IIEriBa2Cu3OT_j [010l or EriBa2Cu3OT_6 [ 100].