Objective To investigate the risk factors affecting the prognosis of children with severe pneumonia below5 years old and provide a theoretical reference for prevention, diagnosis and treatment of severe pneumonia in children. Methods The clinical data, clinical features, complications, and related treatments in 115 children with severe pneumonia in our hospital from October 2016 to October 2018 were retrospectively analyzed. Logistic regression analysis was used to analyze the risk factors for prognosis. Results Among 1115 children with severe pneumonia, there were 42 cases (36.52%) of respiratory acidosis,38 cases (33.04%) of hyponatremia, 37 cases (32.17%) of hypocalcemia, 33 cases of respiratory syncytial virus (28.69%) and 11 cases (9.57%) of Klebsiella pneumonia. Chest X-ray showed patchy shadow in 105 cases (91.30%). In 80 cases of severe pneumonia after treatment was invalid or aggravated. 44 cases(55%) showed pulmonary atelectasis by chest CT examination. 106 children with severe pneumonia had complications. The proportion was as high as 92.17% (106/115), of which 47.17% (50/106) had only one complication, 5283% (56/106) had more than two complications. All the children were treated with antibiotics. The difference in the prognosis of children with and without mechanical ventilation was statistically significant (X2=9.247, P=0.002). The univariate analysis showed that the treatment efficiency was significantly lower in children with severe pneumonia, such as course of disease before admission, transferred to intensive care unit, underlying disease, complications, anemia, electrolyte imbalance, and low serum albumin (P＜0.05). 50 cases (4348%) were finally cured; Multivariate Logistic regression analysis showed that the course of illness before admission, transfer to intensive care unit, underlying disease, complications, anemia, electrolyte imbalance, low albumin were independent risk factors affecting the prognosis of children with severe pneumonia (P＜0.05). Conclusion The condition of children with severe pneumonia is complex and diverse. The course of illness before admission, transfer to intensive care unit, underlying disease, complications, anemia, electrolyteimbalance, low albumin are independent risk factors affecting the prognosis of children with severe pneumonia. The active treatment and symptomatic intervention are of vital importance for improving the prognosis and reducing the mortality of children.