Superconducting YBa2Cu3O7−&dgr;thin films withTc=89.5 K were deposited on MgLaAl11O19(11¯0) substrates by pulsed laser deposition. X‐ray diffraction patterns indicate that the YBa2Cu3O7−&dgr;films were epitaxial films, with thecaxis perpendicular to the substrate surfaces. Microstrip resonators of YBa2Cu3O7−&dgr;thin films deposited on MgLaAl11O19substrates were fabricated. The loaded quality factor of the resonator was 1007 at 77 K and 4.28 GHz. As a new substrate for highTcoxide superconducting films, MgLaAl11O19substrates are especially suitable for superconducting‐microwave applications.