Abstract: Critical intake flow rate is the major data for design and manufacturing of integrated cyclone transmission -separation equipment However, its mechanism has not been fully understood at present, so determination of critical intake flow rate is difficult It is believed based on a-nalysis that intake flow rate and flow velocity can be used to control the relative velocity of two phases and critical intake flow rate of mixed fluid - gas system equipment and correlation formula can be determined, so as to provide theoretical basis for design and manufacturing of integrated caloric transmission - separation equipment.