Objective:To explore the diagnostic value of chest CT imaging in differential diagnosis between common-type COVID-19 and mycoplasma pneumonia (MP).Methods:From the January to February 2020, the clinical and imaging data of COVID-19 patients (diagnosed in the Affiliated Hospital of Jining Medical University, the Fourth People's Hospital of Jining and the Second People's Hospital of Jining) and MP patients (diagnosed in the Affiliated Hospital of Jining Medical University) were retrospectively collected and analyzed. Forty-three patients with common-type COVID-19 (28 males, 15 females, 43±14 years old) and 50 patients with MP (19 males, 31 females, 37±14 years old) were enrolled as COVID-19 group and MP group, respectively. The clinical manifestations, laboratory results and chest CT findings of these two groups were analyzed and compared.Results:(1) Clinical manifestations: there were more patients with muscle ache and asthenia in COVID-19 group than in MP group (χ 2=5.110, 4.834, P<0.05). No significant difference was found in fever and cough between two groups (χ 2=0.378, 0.097, P>0.05). (2) Laboratory examination: the procalcitonin level of cases in COVID-19 group was significantly lower than that in MP group (χ 2=12.263, P=0.001). No significant difference was found in leukocyte count, lymphocyte count, C-reactive protein level and erythrocyte sedimentation rate ( Z=-1.117, χ 2=2.410, 0.787, 0.800, all P>0.05) between two groups. (3) Chest CT findings bilateral lung involvement was found more in COVID-19 group than in MP group (χ 2=30.012, P<0.001); while the one lobe of ipilateral lung involvement was less in COVID-19 group than in MP group (χ 2=19.927, P<0.001); there was no significant difference in multiple lobes of ipilateral lung involvment between the two groups (χ 2=1.366, P>0.05). Ground glass, paving stone sign and air bronchus sign were found significantly more in COVID-19 group than in MP group (χ 2=30.171, 19.119, 9.790, all P<0.05); while the pulmonary consolidation, central lobular nodule and centripetal thickening of bronchus wall were found significantly less in COVID-19 group than in MP group (χ 2=25.450, 33.532, 48.553, all P<0.001). Conclusions:The clinical manifestations and laboratory examination have limited value in the differential diagnosis of common-type COVID-19 and MP, while chest CT imaging might be more valuable in the early differential diagnosis of these two diseases.