Objective:To analyze the clinical characteristics of patients with novel coronavirus pneumonia (COVID-19) and the factors influencing mild cases developing into severe cases, so as to provide a basis for clinical screening, prevention and treatment of potential severe cases.Methods:Retrospective analysis was performed on the clinical characteristics of 168 cases who were admitted to two tertiary general hospitals in Anhui province and diagnosed with COVID-19 from January 20 to March 4, 2020. According to the classification criteria in the COVID-19 diagnosis and treatment program (trial version 6) issued by the National Health Commission, the mild and common cases were classified as the mild group ( n=137), and the severe and critical cases were classified as the severe group ( n=31). The general data, epidemiological history, clinical manifestations, laboratory examination and imaging indexes of the two groups were compared. Univariate analysis was performed. Then multivariate Logistic regression analysis was conducted on the factors with statistically significant differences in univariate analysis to obtain independent influencing factors of the occurrence of severe COVID-19. Results:Among the 168 COVID-19 patients, 95 were male and 73 were female, with an average age of 42.6±15.8 years old. The mean age of the mild group was younger than that of the severe group (40.5±15.5 vs 51.6 ±14.1, P<0.01). The proportion of patients combined with hypertension (29.0% vs 10.9%), diabetes (25.8% vs 2.2%, P=0.005) and two or more underlying diseases (29.0% vs 4.4%, P=0.006) in the severe group were significantly higher than those in the mild group. In the severe group, the proportion of patients receiving initial treatment in Medical institutions below secondary hospitals was significantly higher than that in the mild group ( P<0.01), and the time between symptom onset and diagnosis was longer [(8.00±3.27) d vs (6.49±3.90) d, P=0.048]. There was no significant difference in the initial symptoms between the mild group and the severe group. However, the body temperature was higher in the severe group [(38.80±0.67)℃ vs (37.9±0.60)℃, P<0.01]. At the time of admission, the lymphocyte percentage of the severe group was significantly lower than that of the mild group [(18.20±9.13)% vs (24.43±10.43)%, P<0.01], while C-reactive protein, interleukin-6 (IL-6), D-dimer, LDH, aspartate and aminotransferase were significantly higher than that of the mild group ( P<0.01). CT imaging showed that 11 (8%) patients in the mild group had lesions confined to a single lobe of the lung, while all patients in the severe group had multi-lobe lesions ( P<0.01). All the 168 COVID-19 patients in this study were cured, and the length of hospital stay in the severe group was significantly longer than that in the mild group [(24.71±7.72) d vs (20.28±7.67) d, P=0.021]. According to multivariate binary Logistic regression analysis, age ( P=0.042), diabetes ( P=0.021), body temperature at admission ( P=0.001), and IL-6 measured at admission ( P=0.008) were independent factors affecting COVID-19 to severe progress. Conclusions:Strengthening the professional knowledge training of primary hospitals is helpful for early diagnosis of COVID-19. Patients with older age, combined with diabetes, high initial fever and significantly increased IL-6 level are more possibly to develop into severe disease. Early identification and prevention should be carried out.