This study designed to explore the function and mechanism of NKT cells in asthma, by comparing asthmatic and healthy children in term of the frequency of CD3＋TCRvα24＋NKT cells and the percentages of CD4＋, CD8＋ and CD4-CD8- （DN） subpopulations, as well as the expression of IL-4, IFN-γ and CD69 of every NKT subpopulation in PBMCs. Peripheral blood samples from 12 cases of acute exacerbation of asthma children and 10 cases of healthy control children were collected for preparing PBMCs, then the cell surface markers （CD3＋TCRvα24 CD4, CD8 and CD69） and intracellular cytokines （IL-4 and IFN-γ） of PBMCs were stained for flow cytometry analysis. The average percentages of CD3＋TCRvα24＋ NKT cells from blood of asthmatic and healthy children were 0.42% and 0.32% respectively. Cells could be identified based upon the expressions of CD4 and CD8 molecules. The percentage of CD4＋ NKT was 71.60%, CD8＋ NKT was 14.90% and DN NKT was 12.55% in asthmatic children compared with 63.00%, 13.12% and 22.78% in control. The results showed that children undergoing exacerbations of asthma demonstrated more CD4＋ NKT cells and less DN NKT cells as compared with healthy control children. Furthermore, we found that every subpopulation of CD3＋ TCRvct24＋ NKT could expressed CD69, IL-4, and IFN-γ. The levels of IL-4 and IFN-γ in CD4＋ and DN NKT were higher than those of CD8＋ NKT, and the expression of CD69 detected on DN NKT was more than that on the other two subpopulations. However, no significant difference was found in the expression of IL-4, IFN-γ and CD69 between asthmatic and healthy children. In conclusion, the frequency of CD3＋TCRvα24＋CD4＋ NKT cell is increased, but CD3＋TCRvα24＋DT NKT cells are decreased in blood of asthmatic children compared with healthy children, and the variation of CD3＋TCRvα24＋NKT NKT cells might involve in asthmatic attack and exacerbations.