Clinically, it is defined as novel coronavirus pneumonia severe when any of the following is met: 1. respiratory distress with respiratory frequency ≥ 30 breaths/min; 2. oxygen saturation ≤ 93% at rest; 3. arterial partial pressure of oxygen (PaO2)/inhaled oxygen concentration (FiO2) ≤ 300 mmHg (1 mmHg = 0.133 kPa). For severe cases, on the basis of symptomatic treatment, active prevention and treatment of complications, treatment of underlying diseases, prevention of secondary infections, and timely organ function support are required. At the same time, patients need to be calmed down with anxiety and fear, and psychological guidance needs to be strengthened.