Objective: To explore the application effect of high-sensitivity C-reactive protein detection combined with routine blood tests in differential diagnosis of infectious diseases.Methods: From January 2023 to December 2024, 80 patients with suspected infectious diseases and 80 healthy people were selected from Zhumadian Traditional Chinese Medicine Hospital, and all of them were tested for high-sensitivity C-reactive protein and routine blood tests, and the diagnosis results were analyzed.Results: The combined diagnosis was positive in 63 cases. 17 cases were negative, which was higher than that of 62 cases with high sensitivity C-reactive protein. 18 cases were negative, and 61 cases were positive in routine blood diagnosis. 19 cases were negative. The accuracy of combined diagnosis is 100.00%, and the diagnostic accuracy, specificity and sensitivity of high-sensitivity C-reactive protein are 96.25%, 94.12% and 96.83% higher than those of routine blood diagnosis, 87.50%, 76.47% and 90.48%. The levels of neutrophils, leukocytes and high-sensitivity C-reactive protein in patients with bacterial infection were higher than those in patients with virus infection and healthy people (P < 0.05).Conclusion: Combined diagnosis is effective in differential diagnosis of infectious diseases, and the two kinds of diagnosis can complement each other, which can improve the accuracy of differential diagnosis of diseases and is worth popularizing.