Epstein–Barr virus (EBV) is a globally prevalent herpesvirus associated with multiple diseases. This study aimed to determine the characteristics of primary EBV infection disease spectrum and reactivation in children, in Suzhou, China. All children admitted to the Children's Hospital of Soochow University between May 2018 and September 2020 with suspected EBV‐associated disease and subjected to the indirect immunofluorescence assay for EBV‐specific antibodies and plasma EBV‐DNA assays were included. Of the 3567 children, 2782 (78.0%) tested positive for EBV. The positive rates of viral capsid antigen (VCA)‐IgM, VCA‐IgG, early antigen (EA)‐IgG, nuclear antigen (EBNA)‐IgG, and plasma EBV‐DNA were 12.1%, 74.6%, 37.9%, 35.6%, and 31.1%, respectively. The lowest VCA‐IgG and EBNA‐IgG seropositivity rates occurred at ages between 8 and 36 months, then increased gradually in the older age groups. The EBV‐IgM seropositivity rate was the highest in those aged 36 to <72 months. Primary EBV infection was more common in children aged 36 to <72 months. In past infections, reactivation mainly occurred in 8 to <36 months. The most common disease caused by primary EBV infection was infectious mononucleosis (56.1%), followed by a respiratory infection (17.0%). Respiratory infection (30.0%), EBV infection (29.2%), and hemophagocytic lymphohistiocytosis (HLH) (15.8%) were the commonest diseases caused by EBV reactivation. EBV reactivation was a risk factor for HLH (adjusted odds ratio, 16.4; 95% confidence interval, 7.9–34.0). Among reactivated patients, the viral load of HLH was higher than that of EBV infection and respiratory infection (p < .01). This is a retrospective large sample study that explored the characteristics of primary EBV infection disease spectrum and reactivation in children.