Abstract: To broaden the operating range and improve the thermodynamic performance of heavy-duty gas turbines using hydrogen-ammonia blended fuels, the 255.6 MW heavy-duty gas turbine at Banshan Power Plant was used as the research object. A regulation strategy based on adjusting the inlet guide vane (IGV) angle was proposed to investigate the gas turbine performance, supercritical conditions in turbine stages, and flow matching characteristics under different hydrogen-ammonium blending ratios. Results show that the calculated power and efficiency under the rated operating condition by the established model are 254.59 MW and 36.33% respectively. The relative errors compared to the design values are -0.4% and -1.54% respectively, demonstrating that the model calculations possess sufficient accuracy. When operating with hydrogen-ammonia blended fuels, the Mach number at the exit of the last-stage stator exceeds 1, resulting in potential safety hazards and degraded operational performance. As the ammonia volume fraction increases from 0 to 100%, the IGV angle decreases from 81.41° to 72.77°. After flow matching optimization, the Mach number at the exit of the last-stage stator decreases from 0.97 to 0.86, while the gas turbine efficiency decreases from 37.14% to 36.64%.