The structural properties of a high‐temeprature superconducting textured YBa2Cu3O7−xthin film on a SrTiO3(100) substrate have been studied by reflection x‐ray pole‐figure methods, which can elucidate the degree of preferred orientations of the crystallites in polycrystalline materials and the relative orientations and lateral lattice alignments of the film with respect to the substrate. The specimen was fabricated on a SrTiO3(100) substrate by rf diode sputter deposition and subsequent furnace annealing in flowing oxygen. The film was found to be more preferentiallyaaxis oriented thancaxis oriented with a grain ratio of about 4:1. Thea‐axis‐oriented grains are heavily twinned and the twinning structure is reflection about the (013) plane. The pole figures of thec‐axis‐oriented grains are consistent with the (110) reflection twinning structure. Nevertheless, the crystal axes of both types of oriented grains are aligned with those of the substrate. In addition, the interface matching of the film with respect to the substrate is discussed.