Objective To investigate the correlation between MSCT image signs, clinical pulmonary infection score and severity of severe pneumonia. Methods 54 patients admitted to our hospital from January 2017 to October 2018 were examined by chest MSCT. The clinical and imaging data of 54 patients with severe pneumonia were collected. The clinical pulmonary infection score (CPIS) and APACHE II score of different MSCT image signs of severe pneumonia were compared, and the correlation between MSCT image signs of severe pneumonia and CPIS, APACHE II score was analyzed. Results Among 54 patients with severe pneumonia, 12 patients showed ground glass changes, 26 patients showed pulmonary consolidation, and 16 patients showed patchy shadow changes. Different number of lobes were involved: 16 cases involved one lobe and 38 cases involved more than two lobes. The scores of CPIS and APACHE II in patients with different MSCT image signs and different number of lung lobes were significantly different. The scores of CPIS and APACHE II in patients with lung lobes (≥2) were significantly higher than those in patients with lung lobes (≥1). The scores of CPIS and APACHE II increased with the increase of the number of lung lobes involved (P<0.001). The scores of CPIS and APACHE II in patients with ground glass opacity were lower than those in patients with patchy opacity and pulmonary consolidation (P<0.001). Conclusion MSCT image signs of severe pneumonia are correlated with CPIS and APACHE II scores.