Objective To observe the development of lymphocyte subsets and expression level of platelet associated antibody in children’s peripheral blood with immune thrombocytopenia and explore the associated clinical significance and supply references for the clinic. Methods Ninety-eight children with immune thrombocytopenia admitted to Shenzhen Children^,s Hospital between June 2020 to June 2021 were selected,at the same time twenty-three healthy children were selected as normal controls. By using flow cytometry to detect expression level of lymphocyte subsets and platelet associated antibodies (PAIgG、PAIgM、PAIgA ),at the same time 24 cases were selected to measure platelet associated antibodies before and after treatment, correlation analysis and receiver operating curve(ROC) were used to estimated its guiding role in clinical diagnosis. Results The positive percentage of platelet associated antibodies (PAIgG、PAIgM、PAIgA) were significantly higher in ITP children than healthy controls(P<0.01),then decrease after treatment(P<0.05). Whereas CD16⁺56⁺NK cells were lower than normal controls,the difference was statistically significant(P<0.01).The percentage of CD19⁺B cells、CD3⁺T cells、CD3⁺CD4⁺T cells、CD3⁺CD8⁺T cells and CD3⁺CD16⁺56⁺NKT cells had no significant difference compare to normal controls(P>0.05). A statistically significant negative correlation between PAIgG、PAIgM、PAIgA and change in platelet count was recorded,however,there was no correlation between the percentage of lymphocyte subsets and the decrease of platelet. The area under ROC curve combined with PAIgG、PAIgM、PAIgA and CD16⁺56⁺NK cells to diagnose ITP was 0.876,sensitivity and specificity of platelet associated antibody combined with CD16⁺56⁺NK cells were 93% and 65%. Conclusion Platelet associated antibody and lymphocyte subsets can provide reference for clinical diagnosis and prognosis prediction. The combination of the two methods can improve the sensitivity of the diagnosis of immune thrombocytopenia.