BACKGROUND: To investigate the CT changes of different clinical types of COVID-19 pneumonia. METHODS: This retrospective study included 50 patients with COVID-19 from 16 January 2020 to 25 February 2020. We analyzed the clinical characteristics, CT characteristics and the pneumonia involvement of the patients between the moderate group and the severe and critical group, and the dynamic changes of severity with the CT follow-up time. RESULTS: There were differences in the CT severity score of the right lung in the initial CT, and total CT severity score in the initial and follow-up CT between the moderate group and the severe and critical group (all p < 0.05). There was a quadratic relationship between total CT severity score and CT follow-up time in the severe and critical group (r(2) = 0.137, p = 0.008), the total CT severity score peaked at the second follow-up CT. There was no correlation between total CT severity score and CT follow-up time in the moderate group (p > 0.05). There were no differences in the occurrence rate of CT characteristics in the initial CT between the two groups (all p > 0.05). There were differences in the occurrence rate of ground-glass opacity and crazy-paving pattern in the second follow-up CT, and pleural thickening or adhesion in the third follow-up CT between the two groups (all p < 0.05). CONCLUSIONS: The CT changes of COVID-19 pneumonia with different severity were different, and the extent of pneumonia involvement by CT can help to assess the severity of COVID-19 pneumonia rather than the initial CT characteristics.