Abstract： Objective:To investigate the correlation of blood routine(WBC),C-reactive protein(CRP),serum procalcitonin(PCT)and mycoplasma pneumonia nucleic acid,respiratory virus nucleic acid or antigen positive in respiratory tract infection.Methods:A total of 306 children with respiratory tract infection admitted to Women and Children's of Shandong Province from April 2019 to December 2021 were collected.Venous blood samples were collected to detect blood routine,PCT and CRP,and their correlation was statistically analyzed.Results:There were significant differences in WBC,N%and CRP among influenza B virus,influenza A virus,respiratory syncytial virus and adenovirus(P<0.05).There was no significant difference in PCT among different viruses(P>0.05).There was no significant difference in N%,CRP and PCT3 between mycoplasma nucleic acid positive and virus positive children(P>0.05).There was significant difference in WBC between mycoplasma positive and virus positive children(P<0.05).There was no significant difference in WBC,N%,CRP and PCT between antigen positive and nucleic acid positive children(P>0.05).Conclusion:Among the viral pathogen detection methods,antigen detection or nucleic acid detection can be selected according to the detection conditions of the hospital itself.When the detection results are negative,the application of WBC,NE,CRP detection has certain reference value for the differential diagnosis of different virus and mycoplasma infections.