Objective：To analyze the etiological factor of recurrent lower respiratory tract infection（RLRTI） in children under six years old in Chongqing，so as to provide pediatricians references for diagnosis and treatment. Methods：Clinical data of 417 children under six years old in Chongqing with recurrent RLRTI hospitalized in the respiratory ward of Children’s Hospital of Chongqing Medical University from June 2015 to May 2019 were collected and analyzed retrospectively. The 417 patients were divided into three groups according to ages：the < 1 year old group（197 patients），the 1-3 years old group（129 patients） and the < 6 years old group（91 patients）. Examination results and treating ways in three groups were analyzed. Results：According to results，children < 1 year old had malnutrition（moderate to severe） of 17 cases，gastroesophageal reflux of 30 cases，tracheoesophageal fistula of 9 cases，tracheal ring of 7 cases（3.55%），bronchial softening（moderate to severe） of 11 cases，pulmonary artery sling of 6 cases，congenital heart disease of 70 cases，congenital pulmonary cyst（CPC） of 3 cases and unclear etiology factors of 44 cases. Children between 1-3 years old had cough variant asthma（CVA） of 12 cases，bronchial asthma of 41 cases，primary immunodeficiency disease（PID） of 5 cases，congenital heart disease of 19 cases，congenital pulmonary cyst of 5 cases，bronchial foreign body of 7 cases，occlusive bronchi－olitis of 3 cases，congenital adenomatoid malformation of 2 cas－es，primary ciliary dyskinesia of 5 cases，bronchiectasis of 11 cases and unclear etiology factors of 19 cases. Children between 3-6 years old had CVA of 21 cases，asthma of 37 cases，PID of 5 cases，bronchiectasis of 12 cases，bronchial foreign body of 2 cases，CPC of 1 case，intracranial space-occupying diseases of 1 case and unclear etiology factors of 12 cases. Conclusion：Etiological factors of RLRTI in children under six years old in Chongqing are closely related to age. Patients less than one year old are closely related with congenital dysplasia，while patients over one year old are closely related with asthma.