High flow nasal cannula oxygen therapy (HFNC) is a new type of oxygen therapy. Because of its unique physiological effects, the clinical application is becoming more and more popular. The article summarized HFNC has obvious advantages in oxygenation and comfort. In the clinical, HFNC is widely used in adult patients with acute hypoxemic respiratory failure, respiratory failure after the operation or extubation and respiratory tract invasive operation. But there is no literature reports in improving ventilation to reduce carbon dioxide. If patients′ respiratory, cycle and oxygenation show no significant improvement after application of HFNC for a short time, it should be replaced as soon as possible for the noninvasive and invasive mechanical ventilation. In this article, the characteristic and application of HFNC will be reviewed.