Objective To study diagnosis values of multiple clinical detectors including DNA copies of Epstein-Barr virus (EBV) , antibodies of EB viral capsid antigen (VCA), atypical lymphocytes, white blood cells (WBC) and alanine aminotransferase (ALT) in different fever’s days of children infectious mononucleosis (IM). Methods The relationships were tested between fevers’ days and each value of EBV-DNA, atypical lymphocytes, WBC, ALT and VCA antibody in 101 cases of children IMs by scatter plot analysis. Results The results indicated the trends were different among multiple clinical detectors. Detection rates of EBV-DNA and IgG-VCA in early and mid-fever stage (within 8 fevers’ days) were relatively high (77.2% and 76.9% respectively). The two dectectors went down dramatically after fever 12 days. Conclusions Detection of EBV-DNA in early fever stage and IgG-VCA in mid-fever stage in children have high values for diagnosis of IM.