Abstract: Objective　To investigate dynamic changes of the number of peripheral blood atypical lymphocyte and T-lymphocyte subsets in children with acute rotavirus（RV） diarrhea. Methods　A total of 40 children with acute RV diarrhea and 20 healthy controls were enrolled in this study. The proportions of peripheral blood atypical lymphocytes in their peripheral blood smear with Wright stain were figured out by microscopy. Meanwhile，the T-lymphocyte subsets were examined by flow cytometry. Results　The proportion of peripheral blood atypical lymphocytes was 16.18%±3.59% in children with acute RV diarrhea and had an obviously increase compared with that in healthy controls（P＜0.001）. The percentages of CD3⁺，CD4⁺ and CD8⁺T cells in peripheral blood of children with acute RV diarrhea and CD4⁺/CD8⁺ ratio were 50.93%±5.86%，22.02%±5.17%，27.07%±4.79% and 0.84%±0.29% respectively. Compared with the healthy controls，the infected groups had a decreased percentage of T cells（P＜0.01）. Conclusions　There are the increasing of atypical lymphocyte number and atypical T-lymphocyte subsets in children with acute RV diarrhea. The determination of atypical lymphocyte number and T-lymphocyte subsets could satisfactorily reflect the immunological state in children with acute RV diarrhea.