Objective：To analyze the clinical features of children with purulent meningitis（PM） complicated with subdural effusion（SE），and to search for the indicators of the early diagnosis for PM complicated with SE. Methods：A retrospective study was conducted among 258 children（129 children were diagnosed as PM complicated with SE，while the other randomly selected 129 children were diagnosed as PM only）. T test/Chi-square test/rank sum test and logistic regression analysis were used to explore the clinical features. Results：The most common clinical features were：fever，convulsion，vomiting，and bulging fontanelle，etc. The incidences of subdural effusions were closely correlated with the bulging font-anelle on admission，cerebrospinal fluid（CSF） glucose concentration on admission，and CSF white blood cell（WBC） counts on admission. Conclusion：There is no specific clinical manifestation in SE；clinical outcomes and auxiliary examinations can guarantee the right diagnosis. Those infants who have bulging anterior fontanelle on admission，CSF glucose concentration lower than 1.5 mmol/L，and CSF WBC count over than 200×106/L may develop SE.