Objectives To investigate CT images of 100 confirmed COVID-19 pneumonia patients to describe the lesion distribution, CT signs, and evolution during different courses. Methods A retrospective study of 100 COVID-19 pneumonia patients without ARDS was performed, and CT scans were reviewed. A COVID-19 pneumonia course diagram was drawn. Mann-Whitney U test was used to compare the lesion distribution and CT scores, chi(2) test was used to compare the CT findings between different stages. Results A total of 272 CT scans from 100 patients (mean age, 52.3 years +/- 13.1) were investigated. Four patients with lung abnormalities on CT first showed negative RT-PCR result and turned positive afterwards. One hundred sixty-nine (62.1%) showed predominantly peripheral distribution. The CT scores of the upper zone (3.4 +/- 3.6) were significantly lower than those of the middle (5.0 +/- 3.9) and lower (4.8 +/- 3.6) zones (p < 0.001). The CT scores of the anterior zones (4.9 +/- 4.7) were significantly lower than those of the posterior zones (8.4 +/- 6.2) (p < 0.001). In the early rapid progressive stage (1 similar to 7 days), ground glass opacity (GGO) plus reticular pattern (58.1%), GGO plus consolidation (43.0%), and GGO (41.9%) were all common. In the advanced stage (8 similar to 14 days), GGO plus consolidation (79.8%) and repairing CT signs (subpleural line, bronchus distortion, and fibrotic strips) showed a significant increase (p < 0.05). In the absorption stage, GGO plus consolidation (9.1%) sharply decreased (p < 0.05). Conclusion CT imaging of COVID-19 pneumonia showed a predominantly peripheral, middle and lower, and posterior distribution. The early rapid progressive stage is 1 similar to 7 days from symptom onset, the advanced stage with peak levels of abnormalities on CT is 8 similar to 14 days, and the abnormalities started to improve after 14 days.