High flow nasal oxygen therapy (HFNO) is an emergent oxygen delivery device that gained attention from clinicians because of its specific action mechanisms and physiological effects. This review summarizes research advances related to HFNO in recent years and reviews the clinical application of HFNO in patients with respiratory insufficiency, peri‑anaesthesia and COVID‑19. The effects of HFNO on respiratory function, tracheal intubation rate, apneic oxygenation, and pulse oxygen saturation (SpO2) were analyzed when compared with noninvasive ventilation, nasal cannula, and mask ventilation. It provides a theoretical basis for the clinical application of HFNO.