Objective:To explore the correlation between the ratio of C-reactive protein (CRP) to albumin (CAR) and the syndrome type of Wei-Qi-Ying-Xue in patients with severe coronavirus disease 2019 (COVID-19).Methods:A case-control study was conducted to select 63 severe patients with COVID-19 admitted to the Dongzhimen Hospital of Beijing University of Chinese Medicine from December 2022 to December 2023, including 50 severe cases and 13 critical cases. The clinical data of the patients were collected. According to the syndrome differentiation of Wei-Qi-Ying-Xue, there were 21 cases of Qi syndrome, 20 cases of Ying syndrome and 22 cases of Xue syndrome. The differences of CRP, ALB and CAR levels in patients with different Wei-Qi-Ying-Xue syndromes were compared. Spearman correlation test was used to test the correlation between CRP, ALB, CAR and the Wei-Qi-Ying-Xue syndrome type, and the receiver operating characteristic (ROC) curve was used to detect the diagnostic efficacy of CRP, ALB and CAR on the Wei-Qi-Ying-Xue syndrome type.Results:There was a statistically significant difference in the clinical classification of Western medicine among the three groups ( P<0.05). The CAR of the Ying group and the Xue group was higher than that of the Qi group ( P<0.05), while there was no statistically significant difference in age and comorbidities (all P>0.05). The CRP of the Xue group was higher than that of the Qi group ( P<0.05), and the ALB of the Ying group and the Xue group was lower than that of the Qi group (all P<0.05). Correlation analysis showed that there was a correlation between the Wei-Qi-Ying-Xue syndrome type and CRP, ALB and CAR ( P<0.05), among which CAR changed most significantly with the change of Wei-Qi-Ying-Xue syndrome type. ROC curve analysis showed that CRP, ALB and CAR had good diagnostic value for Qi syndrome and Xue syndrome ( P<0.05). The critical values of the diagnosis of Qi syndrome were 48.57 mg/L, 34.20 g/L and 2.97. The critical values of the diagnosis of Xue syndrome were 28.30 mg/L, 26.6 g/L and 5.96. Conclusions:CAR ratio is correlated with the Wei-Qi-Ying-Xue syndrome type of severe COVID-19 patients, and its level changes are in line with the evolution law of Wei-Qi-Ying-Xue syndrome. CAR≤2.97 is contributed to the diagnosis of Qi syndrome, and CAR>5.96 is contributed to the diagnosis of Xue syndrome. CAR may be an objective index related to the Wei-Qi-Ying-Xue syndrome type of severe COVID-19 patients.