This study aimed to investigate the clinical and CT features associated with severe and critical COVID-19 pneumonia. A total of 83 patients with COVID-19 pneumonia were enrolled, including 25 severe/critical cases and 58 ordinary cases. The clinical data and chest CT images of these patients were reviewed and compared. The risk factors associated with disease severity were analyzed. Severe/critical patients were significantly older, had more comorbidities, and exhibited higher incidence of cough, expectoration, chest pain, and dyspnea compared to ordinary patients. CT findings showed that severe/critical patients had higher incidence of consolidation, linear opacities, crazy-paving pattern, and bronchial wall thickening. Additionally, they showed higher incidence of lymph node enlargement, pericardial effusion, and pleural effusion. The CT scores of severe/critical patients were significantly higher than those of ordinary patients. The CT score had a high sensitivity and specificity for distinguishing severe/critical cases from ordinary cases. Clinical factors associated with severe/critical COVID-19 pneumonia included age over 50 years, comorbidities, dyspnea, chest pain, cough, expectoration, decreased lymphocytes, and increased inflammation indicators. CT findings such as consolidation, linear opacities, crazy-paving pattern, bronchial wall thickening, high CT scores, and extrapulmonary lesions were features of severe/critical COVID-19 pneumonia. The study concluded that there are significant differences in clinical symptoms, laboratory examinations, and CT manifestations between ordinary and severe/critical patients. Many factors are related to the severity of the disease, which can help clinicians judge the severity of the patient and evaluate the prognosis. Chest CT plays an important role in the diagnosis and evaluation of disease severity for COVID-19 pneumonia. However, the study has limitations, including unbalanced data between the two groups and a relatively small sample size of severe/critical patients. Further studies with larger samples are needed.This study aimed to investigate the clinical and CT features associated with severe and critical COVID-19 pneumonia. A total of 83 patients with COVID-19 pneumonia were enrolled, including 25 severe/critical cases and 58 ordinary cases. The clinical data and chest CT images of these patients were reviewed and compared. The risk factors associated with disease severity were analyzed. Severe/critical patients were significantly older, had more comorbidities, and exhibited higher incidence of cough, expectoration, chest pain, and dyspnea compared to ordinary patients. CT findings showed that severe/critical patients had higher incidence of consolidation, linear opacities, crazy-paving pattern, and bronchial wall thickening. Additionally, they showed higher incidence of lymph node enlargement, pericardial effusion, and pleural effusion. The CT scores of severe/critical patients were significantly higher than those of ordinary patients. The CT score had a high sensitivity and specificity for distinguishing severe/critical cases from ordinary cases. Clinical factors associated with severe/critical COVID-19 pneumonia included age over 50 years, comorbidities, dyspnea, chest pain, cough, expectoration, decreased lymphocytes, and increased inflammation indicators. CT findings such as consolidation, linear opacities, crazy-paving pattern, bronchial wall thickening, high CT scores, and extrapulmonary lesions were features of severe/critical COVID-19 pneumonia. The study concluded that there are significant differences in clinical symptoms, laboratory examinations, and CT manifestations between ordinary and severe/critical patients. Many factors are related to the severity of the disease, which can help clinicians judge the severity of the patient and evaluate the prognosis. Chest CT plays an important role in the diagnosis and evaluation of disease severity for COVID-19 pneumonia. However, the study has limitations, including unbalanced data between the two groups and a relatively small sample size of severe/critical patients. Further studies with larger samples are needed.