ObjectiveTo investigate the etiology of infectious pleural effusion in children，and provide ideas and methods for the diagnosis and treatment of infectious pleural effusion．Methods165 children diagnosed with pleural effusion by chest radiography and (or) ultrasound B were admitted to a hospital from January 2011 to December 2012, their clinical and laboratory data were analyzed retrospectively．ResultsOf 165 children, 146(88.48%) were with infectious pleural effusion, including Mycoplasma infection 77 cases (52.74％), mixed infection of Mycoplasma and other pathogens 24 cases (16.44%, mixed infection with bacteria, virus and tuberculosis were 17, 6 and 1 respectively), bacterial infection 23 cases (15.75％) （12 cases were tuberculosis infection），viral infection 7 cases (4.79%), paragonimus infection 1 case (0.69%), and unidentified pathogens 14 cases (9.59%). The constituent ratio of Mycoplasma mixed infection in 1-15 years old children was 13.46%-26.32%; tuberculosis infection was highest in 7-15 years old children (19.23%); the ratio of bacterial and viral infection in children aged<1 year was 37.50% and 18.75% respectively.ConclusionMycoplasma infection is the most common cause of infectious pleural effusion in children; especially in 1-15 years old children; bacterial infection is the major cause of pleural effusion in children aged <1 year; tuberculosis infection is common in 7-15 years old children.