Objective: Corticosteroid-resistant secondary immune thrombocytopenia (ITP) is a challenging condition in clinical practice. This study aimed to explore the clinical and immunological characteristics of corticosteroid-resistant secondary ITP associated with connective tissue diseases (CTD-ITP). Methods: We conducted a retrospective analysis of 201 CTD-ITP patients hospitalized between 2014 and 2022. Patients were categorized as corticosteroid-resistant or corticosteroid-sensitive, and their clinical, immunological, and demographic data were compared. Logistic regression analysis was employed to identify independent predictors of corticosteroid resistance. Results: Corticosteroid resistance was observed in 27.4% of patients. Compared with the sensitive group, the resistant group exhibited a higher percentage of CD3⁺T cell (71.38% versus 64.70%, p=0.004) and CD3⁺CD8⁺T cell (38.55% versus 28.95%, p=0.003), but a lower percentage of CD3⁻CD19⁺ B cell (13.70% versus 22.45%, p=0.001) in peripheral blood. No significant differences were found in demographics, clinical features, or autoantibody profiles. And the multivariable logistic regression analysis showed that percentage of CD3⁺CD8⁺T cells (OR=1.117, 95% CI: 1.014-1.350, p=0.031) was independent risk factors for corticosteroid resistance in CTD-ITP patients. Conclusion: This study highlights the role of CD3⁺CD8⁺T cells in corticosteroid resistance among CTD-ITP patients, suggesting that cellular immunity plays a key role in this resistance and providing potential biomarkers for personalized treatment strategies.