Abstract: In the field of gas isotope separation, it is necessary to accurately measure the gas flow in the system. To meet the design requirements, the accuracy of 0.1 mg/s even needs to be achieved at some key positions. In order to control the flow accurately, the principle of “sound velocity orifice plate” in gas hydrodynamics has been widely used in the field of gas isotope separation. Based on the physical principle of sound velocity orifice plate, this paper introduces several commonly used orifice calibration methods, and sorts out the basic application direction, so as to facilitate the majority of scientific researchers to use directly in the process of experimental research and engineering design, etc.