Chronic immune thrombocytopenia (CITP) is an autoimmune disease with many immune dysfunctions, including T helper type 17 cell (Th17)/regulatory T cells (Tregs) imbalance. Low quality of life and side effects of drugs are severe, especially in pediatrics. This study aimed to determine Th17/Treg polarization in pediatric CITP when first diagnosing ITP and evaluate its use as a predictive marker for pediatric CITP. This was a pilot study from a multi-center. Setting the effective data size to 100 patients, data entry ended in the 142nd patient who had completed a 1-year follow-up. The percentages of Treg cells and Th17 cells were quantified by flow cytometry when new diagnosed ITP patients first arrived. The association between the Th17/Treg ratio and CITP was analyzed statistically. The percentages of Treg cells and Th17 cells were lower (P = 0.0008) and higher (P = 0.0001), respectively, in the CITP-outcome group compared with the remission group. The receiver operating characteristic analysis showed that the area under the curve (AUC) of Treg and Th17 cells was 0.811 and 0.834, respectively. The ratio of Th17/Treg exhibited the largest AUC of 0.897 (cutoff value 0.076). Conclusions: Thus, the percentage of Th17/Treg ratio of pediatric CITP is elevated at new diagnosed ITP stage. It is a promising predictive marker for the development of CITP to some extent.