Objective To explore the mixed infection of bacteria and viruses of community-acquired pneumonia (CAP) in children. Methods A total of 204 children with CAP were tested for sputum bacteria, viruses and atypical pathogen, and children with bronchoscope indications were performed with bronchoscope for alveolar lavage (BAL), and the BAL lfuid (BALF) was subjected to quantitative culture and intracellular bacteria detection. All the children were given antimicrobial sequential therapy. Results There were 153 strains of pathogenic bacteria isolated in 122 cases, the detection rate was 59.80%(122/204). Thirty cases were found with mixed bacterial and viral infections. BAL was performed on 70 cases, positive lavage germiculture were detected in 8 cases, of theses BALF specimen inducible co-stimulator (ICOS) positivity were found in 5 cases. Using BALF quantitative culture as control, the sensitivity of ICOS in the diagnosis of CAP was 37.50%and the speciifcity was 96.77%. In 30 cases of mixed infection with bacteria and viruses, 27 cases were younger than 5 years old, accounting for 90.00%. Duration of fever greater than 10 d in mixed infection group of children (43.33%, 13/30) was higher than that of the non-mixed infection group (23.12%, 40/173) (P??0.05). Average hospitalization time in children with mixed infection (13.5+1.5) d was higher than that with non-mixed infection (8.6+1.1) d (P?