Objective To investigate the levels and function status of CD4CD25FOXP3 T cells (CD25 Tregs) in the peripheral blood and synovial fluid from rheumatoid arthritis (RA) patients, and their relationships with disease activity. Methods The study enrolled 60 RA patients and 69 healthy controls (HCs). Flow cytometry was used to analyze the percentage and phenotype of CD25 Tregs, and the results were analyzed by Mann-Whitey U test and Spearman correlation. Results The percentage of circulating CD25 Tregs in CD4 cells was compared between RA patients and HCs. However, the percentage of CD25 Tregs in RA synovial fluid was significantly higher than that in the peripheral blood of RA patients and HCs. When RA patients were grouped according to their disease activity or clinical indicators, such as rheumatoid factor (RF), anti-cyclic citrullinated peptides (CCP) antibody, anti-mutated citrullinated vimentin (MCV) antibody and anti-keratin antibody (AKA), circulating CD25 Tregs percentage was not significantly different among the groups, and had no correlation with the levels of erythrocyte sedimentation rate (ESR) and C reactive protein (CRP). The expression of CD39 in CD25 Tregs in RA synovial fluid was significantly lower than that in the peripheral blood of HCs. And CD73 and TGF-β1 expression in CD25 Tregs in RA synovial fluid were significantly lower than those in the peripheral blood of both RA patients and HCs. However, there was no significant difference in the expression of CTLA4 and IL-10 in CD25 Tregs among the groups. Conclusion The percentage of CD25 Tregs increases in RA synovial fluid. And the expression of CD39, CD73 and TGF-β1 decrease in CD25 Tregs, suggesting that its inhibitory function may be defective, resulting in local inflammation not being effectively controlled.