〔Abstract〕 Objective To explore the value of procalcitonin (PCT), C-reactive protein (CRP) and serum amyloid A (SAA) in differentiating initial bacterial pneumonia infection from viral pneumonia infection. Methods 91 patients with pneumonia treated in Zengcheng District People's Hospital of Guangzhou from January 26, 2020 to April 26, 2020 were selected. 45 patients with bacterial infection were included in group A and 46 patients with virus infection were included in group B. The PCT, CRP and SAA indexes of the two groups were detected, and the differences of relevant indexes and the diagnostic accuracy of the two groups were observed. Results The indexes of serum PCT, CRP and SAA in group A were significantly higher than the normal range, and the indexes of SAA in group B were significantly higher than the normal range. The levels of PCT, CRP and SAA in group B were significantly lower than those in group A, and the ratio of SAA / CRP was significantly higher than that in group A (P < 0.05). The accuracy of diagnosing pneumonia infection by PCT and CRP in group A was higher than that in group B (P < 0.05); The accuracy of combined SAA in the diagnosis of pneumonia infection was higher, but there was no significant difference between the two groups (P > 0.05). Conclusion The detection of serum PCT, CRP and SAA in patients with early pneumonia infection can effectively diagnose bacterial infection. Combined with SAA index detection and SAA / CRP ratio analysis, we can make differential diagnosis of viral infection, clarify the etiology of pneumonia infection, and provide scientific basis for clinical diagnosis and treatment.