Objective To analyze the value of T lymphocyte subsets and Epstein-Barr virus（EBV）-DNA detection in the diagnosis and treatment of infectious mononucleosis（IM） in children. Methods Ninety-eight children with IM admitted to Huanghe Sanmenxia Hospital from December 2018 to December 2020 were selected as the study group

and 80 normal children who underwent physical examination in the hospital during the same period were selected as the control group. The expression of T lymphocyte subsets（CD4

+

CD8

+

CD4

+

/CD8

+

） and EBV-DNA in the two groups were compared

and the changes of T lymphocyte subsets and EBV-DNA in children with IM before and after treatment were analyzed. The correlation between the two groups and the diagnostic value of the two for IM were analyzed. Results The levels of CD4

+

and CD4

+

/CD8

+

in the study group were lower than those in the control group

and the positive expression rate of EBV-DNA and CD8

+

levels were higher than those in the control group

with statistically significant differences（P

<

0.05）. After treatment

the levels of CD4

+

and CD4

+

/CD8

+

in children with IM were significantly higher than those before treatment

and the positive expression rates of EBV-DNA and CD8

+

levels were significantly lower than those before treatment（P

<

0.05）. CD4

+

and CD4

+

/CD8

+

levels were negatively correlated with EBV-DNA positive expression rates（r=-0.304

-0.348

both P

<

0.001）

and CD8

+

levels were positively correlated with EBV-DNA positive expression rates（r=0.342

P

<

0.001）. The area under the curve（AUC） value of combined detection of T lymphocyte subsets and EBV-DNA for the diagnosis of IM was 0.968

which was higher than that of T lymphocyte subsets and EBV-DNA single detection（0.924

0.801）. Conclusion The detection of T lymphocyte subsets and EBV-DNA is of great value in the diagnosis and treatment guidance of IM in children

and the diagnostic efficacy of the combined detection of T lymphocyte subsets and EBV-DNA is higher.