Abstract: Objective: To analyze and compare chest computed tomography (CT) findings and evolutionary characteristics of different strains of novel corona virus pneumonia and to explore the correlation of CT findings and strain characteristics with clinical outcomes. Methods: Chest CT images of 75 cases of the original strain, 130 cases of the Delta variant, and 562 cases of the Omicron variant from the Inner Mongolia Autonomous Region, were collected and sorted. The CT manifestations and their changes for different strains were analyzed and compared. Results: The proportion of patients with mild disease in the Omicron variant group (499 cases, 88.79%) was significantly higher than that in the original strain (9 cases, 12.00%) and Delta variant groups (47 cases, 36.15%). Compared to the original strain group, the Delta variant group showed higher incidences of mild cases% (47 cases, 36.15% vs. 9 cases, 12.00%) and lower incidences of severe cases (14 cases, 16.87% vs. 19 cases, 28.79%). A total of 96.97% (64 cases) of the original strain group, 93.98% (78 cases) of the Delta variant group, and 98.41% (62 cases) of the Omicron variant group showed ground-glass opacities, which were the main manifestations on the first CT scan. There was no statistically significant difference among the three groups. In terms of morphology and distribution of ground-glass opacity, 12 cases (19.05%) of the Omicron group showed acinular nodule ground-glass opacity, which was significantly higher than that shown by the original strain group (2 cases, 3.03%) and the Delta variant group (3 cases, 3.61%). The lesions in the three groups were mainly distributed along the subpleural lung regions. However, the Omicron variant group had a higher distribution ratio along the bronchial vascular bundle than the original strain and Delta variant groups. In terms of concomitant signs, concomitant consolidation and cable proportion were significantly lower on the first CT image. The proportions of concurrent consolidation in the original strain, Delta variant, and Omicron variant groups were 3.03% (2 cases), 6.02% (5 cases), and 5.00% (1 case), respectively. The proportions of accompanying cables in the original strain, Delta variant, and Omicron variant groups were 12.12% (8 cases), 15.66% (13 cases), and 20.00% (4 cases), respectively. The imaging findings of the lesions in the original strain and Delta variant groups changed over the course of the disease. In the original strain group, 39.39% (26 cases) had realistic changes based on the original ground-glass opacity and 53.03% (35 cases) had a cord based on the original ground-glass opacity. This proportion was significantly higher than the proportion of consolidation and cord based on the first CT. In the Delta variant group, 44.58% (37 cases) of patients showed inflammatory consolidation based on the original ground-glass opacity and 61.45% (51 cases) of patients showed a cord based on the original ground-glass opacity. In the Omicron variant group, 34.38% (11 cases) had inflammatory consolidation based on the original ground-glass opacity and 71.88% (23 cases) had cord based on the original ground-glass opacity, both of which were significantly higher than the proportions of primary inflammatory consolidation and cord. The median number of days from apparent absorption to onset in the original strain, Delta variant and Omicron variant groups were 16 days, 16 days, and 9 days, respectively. Conclusions: The dynamic changes in chest CT findings of cases infected with different strains of COVID-19 can reflect the evolution of lesions with the clinical course of the disease. This prediction has clinical application value in determining the course of COVID-19 and disease management.