Objective: To explore the effect of early warning nursing on the prognosis of severe pneumonia patients in intensive care unit (ICU). Methods: Fifty severe pneumonia patients with mechanical ventilation admitted to ICU from January 2017 to May 2018 in Beijing Longfu Hospital were selected as the control group, the patients were given routine nursing. Sixty severe pneumonia patients with mechanical ventilation and mechanical ventilation in the same dapartment from June 2018 to November 2019 were selected as the observation group, and the patients were given severe early warning nursing. The prognosis of the two groups was compared. Results: The Acute Physiology and Chronic Health Evaluation II (APACHE II) score and Murray lung injury score of the observation group were lower than those of the control group; the oxygenation index of the observation group was higher than that of the control group; the mechanical ventilation time and ICU hospitalization time of the observation group were shorter than those of the control group, and the weaning success rate was higher than that of the control group; the differences were all statistically significant (P<0.05 or P<0.01). The total incidences of ventilator associated pneumonia (VAP), atelectasis and deep venous thrombosis (DVT) of the observation group were lower than that of the control group; the differences were statistically significant (P=0.035). Conclusion: Early warning nursing can improve the pathophysiological status of severe pneumonia patients with mechanical ventilation, reduce complications, and shorten the time of mechanical ventilation and admission to ICU.