Objective：To analyze the expression of C-C motif chemokine receptor 8（CCR8）in tumor-infiltrating regulatory T（Treg） cells in ovarian cancer and to investigate the role of CCR8 in Treg cell differentiation. Methods：An ID8 ovarian cancer cell-bearing model was established in C57BL/6 mice. The flow cytometry was used to detect the expression proportion of CCR8 on Treg in mouse tumor tissues，spleens and peripheral blood，and the expression levels of programmed cell death protein 1（PD-1），cytotoxic T-lymphocyte antigen 4（CTLA-4），inducible T-cell costimulator（ICOS）and lymphocyte-activation gene 3（LAG-3）on CCR8⁺ Treg cells. The flow cytometry was also used to detect the changes in the differentiation ratio of naive CD4⁺ T cells to Treg cells in the spleens of C57BL/6 mice before and after the addition of the CCR8 conformational inhibitor AZ084. Results：The expression of CCR8 on Treg cells in the tumors of ovarian cancer -bearing mice was significantly higher，compared with that in the spleens and peripheral blood. Compared with CCR8^- Treg cells，CCR8 ⁺ Treg cells also had a higher expression of immune checkpoint related proteins. AZ084 effectively inhibited the differentiation of naive CD4 ⁺ T cells into Treg cells in the mouse spleens. Conclusion：CCR8 ⁺ Treg cells constitute the major proportion of tumor-infiltrating Treg cells，and CCR8 acts as a primary marker of ovarian cancer-infiltrating Treg cells. Conformational modulation of the CCR8 protein can inhibit the differentiation ratio of Treg cells. The targeted elimination of CCR8⁺ Treg cells may provide new insights for improving the immunosuppressive state of tumor microenvironment in ovarian cancer.