Objective:To analyze the colonization status of Haemophilus influenzae in nasal cavity and oropharynx of children with Mycoplasma pneumoniae pneumonia(MPP)and its clinical significance.Methods:In 80 children with MPP,multiple polymerase chain reaction(PCR)and NGS sequencing were used to detect the common bacteria in the nasal cavity and oropharynx of the enrolled children,and the colonization status of Haemophilus influenzae in children with MPP of different ages and genders was analyzed.Ac-cording to the results of oropharyngeal bacteria detection,the children were divided into MPP group(negative oropharyngeal bacteria)and MPP+bacteria group(positive oropharyngeal bacteria).The clinical characteristics and treatment methods of the two groups were compared.Results:A total of 452 strains of bacteria were isolated from nasal and oropharyngeal secretions of 80 children with MPP.Haemophilus influenzae was the most common colonized strain,and 163 strains were isolated,accounting for 36.06％.Other major strains included Streptococcus pneumoniae(98 strains,21.68％),Staphylococcus aureus(83 strains,18.36％),Escherichia coli(46 strains,10.18％)and Klebsiella pneumoniae(25 strains,5.53％).The colonization rate of Haemophilus influenzae in children aged 1～3 years was the highest,reaching 76.67％(P＜0.05).The colonization rate of Haemophilus influenzae in boys(64.44％)was higher than that in girls(40.00％)(P＜0.05).The duration of fever,duration of cough and hospitalization time in MPP+bacteria group were significantly longer than those in MPP group(P＜0.05).Compared with the MPP+bacterial group,the duration of antibiot-ic use in the MPP group was significantly shorter(P＜0.05),and the proportion of atomization treatment was lower(P=0.027＜0.05).There were no statistical differences in the use of fiberoptic bronchoscopy and use of oxygen therapy between both groups(P＞0.05).Conclusion:There is a high colonization rate of Haemophilus influenzae in nasal cavity and oropharynx of children with MPP,and the colonization status of children with MPP is closely related to the aggravation of the disease,the prolongation of hospitalization time and the increase of treatment demand.