Objective To explore the clinical characteristics, diagnosis and treatment of primary chylopericardium in children. Methods　The clinical data of primary chylopericardium in a child were analyzed retrospectively. And the key words of “children primary chylopericardium”, “pediatric primary chylopericardium” were used to search in Wanfang database, CNKI and PubMed to collect and analyze the reported cases of primary chylopericardium in children at home and abroad. Results　A girl, aged 3 years and 11 months, had cough, chest tightness, chest pain and dyspnea. The girl also had dilated cardiac dullness, distant heart sounds, regular cardiac rhythm, and no murmurs. Chest radiograph showed an enlarged heart shadow and color Doppler echocardiography indicated a large amount of pericardial effusion. Chylous fluid was drained by pericardiocentesis. After symptomatic support treatment, the child's condition improved, but there was still fluid in the pericardial cavity. The amount of pericardial effusion decreased gradually during the follow-up of more than one year, and the child had no special discomfort. Conclusion　Primary chylopericardium is rare in children. It is necessary to be alert of it when dyspnea and distant cardiac sound occur for unknown reasons, and pericardiocentesis is needed for diagnosis.