The millimeter wave irradiation characteristics of a Tl-2212 high-temperature superconducting thin film bicrystal Josephson junction embedded in a hemispherical Fabry-Perot resonator was studied. The coupling characteristics of the bicrystal Josephson junction with the Fabry-Perot resonator have been investigated experimently, showing that it was greatly affected by the factors such as the location of the sample in the open resonator, the angle between them, the pattern of the junction and the distance between the two reflecting mirrors of the resonator. The optimized coupling between Josephson junction and applied microwave was achieved by refined adjustment of the factors. In this case, 9 orders distinct Shapiro steps were observed. Taking advantage of the Fabry-Perot resonator technique, the coupling problem between high-temperature superconducting thin film Josephson junction and applied millimeter wave was well solved, which is of significance for the research on radiation and detection of millimeter wave and terahertz wave of high-temperature superconducting Josephson junction.