BACKGROUND The aim of this study was to determine the effect of C-reactive protein (CRP), lymphocytes (LYM), and the ratio of CRP to LYM (CRP/LYM) on assessing the prognosis of COVID-19 severity at early stages of disease. MATERIAL AND METHODS A total of 108 hospitalized patients diagnosed with COVID-19 in Zhongnan Hospital of Wuhan University from January 17, 2020 to March 12, 2020 were enrolled. Data of demographic parameters, clinical characteristics, laboratory indicators, clinical manifestation, and outcome of disease were collected. The patients were divided into a severe group and a non-severe group according to diagnosis and classification, which followed the guidelines and management of the Chinese National Health Council COVID-19. The receiver-operating characteristic (ROC) analysis and comparison of ROC curves were used for the laboratory findings for assessment of COVID-19 severity. RESULTS Of the 108 patients, 42 patients (38.9%) were male and 24 patients (22.2%) were considered severe cases, with the mean age of 51.0 years old. Males and patients with comorbidities were more likely to become severe cases. CRP increased and LYM decreased in the severe group.The results for the areas under the curve (AUC) of CRP/LYM and CRP used to assess severe COVID-19 were 0.787 (95% CI 0.698-0.860, P<0.0001) and 0.781 (95% CI 0.693-0.856, P<0.0001), respectively; both results were better than that of LYM. The associated criterion value of CRP/LYM was calculated, with an excellent sensitivity of 95.83%. CONCLUSIONS The effect of CRP/LYM and CRP on the assessment for severe COVID-19 may be superior to LYM alone. CRP/LYM is a highly sensitive indicator to assess the severity of COVID-19 in the early stage of disease.