High-temperature, high-pressure gas flow is one of the key parameters measured in aero-engine and heavy-duty gas turbine testing. Calibrating flow meters under the conditions which close to actual operating environments is the most effective method to improve measurement accuracy. In response to the lack of domestic traceability standards for high-temperature, high-pressure gas flow, The High-Efficiency Low-Carbon Gas Turbine Test Facility has planned and constructed China's first high-pressure gas flow standard transfer apparatus. It covers ambient, medium- temperature (100–300°C), and high-temperature (300–600°C) ranges, with a working pressure of 0.4–4.0 MPa, a flow calibration range of 0.05–68 kg/s, and a designed uncertainty of ±0.1% to ±0.5%.