Objective：The aim of our study is to investigate the alterations in frequency of regulatory T cells (Treg cells) and Thelper 17 (Th17) cells in peripheral blood in patients with Crohn’s disease (CD) and the relationship between the proportion of Treg cells and clinical features of CD. Methods: Forty-six patients with CD (31 quiescent and 15 active CD patients) were enrolled in our study． Eight cases who had gastrointestinal polyps treated and will have gastrointestinal endoscopy to check as normal controls. The disease activity of CD was evaluated by Crohn’s disease activity index (CDAI). Concurrently, blood platelet (PLT), mean platelet volume (MPV), platelet distribution width (PDW), erythrocyte sedimentation rate (ESR) and serum C-reactive protein (CRP) level were measured. The percentage of Treg and Th17 cells in peripheral blood from CD patients and control group were detected by flow cytometry. We also analyzed the relationship between the proportion of Treg cells and these inflammatory biomarkers. Results: In peripheral blood, the propotion of Treg cells in active CD patients was significantly decreased compared with patients in remission and control group (P < 0.05). Compared with quiescent CD patients, active CD patients had higher percentage of Th17 cells in peripheral blood (P< 0.05). ESR and serum CRP levels increased and MPV obviously decreased in active CD patients compared to quiescent patients. Negative correlation was found between proportion of Treg cells and ESR, serum CRP levels as well as CDAI (P < 0.05). In addition, there was a positive correlation between the proportion of Treg cells and MPV (P < 0.05)． Conclusion: The change of proportion of Treg and Th17 cells in peripheral blood and the relationship between the proportion of peripheral Treg and serum inflammatory biomarkers reflecting CD activities (e.g., CRP, ESR and MPV) indicate that the differentiation imbalance of Th17/Treg may be involved in the pathogenesis of CD.