Objectives To investigate the effect of rhein on endothelial plasminogen activator inhibitor-1 (PAI-1) mRNA expression and protein production induced by transforming growth factor β1 (TGFβ1), and to explore the mechanism of the protective action of rhein on endothelial cells. Methods A human umbilical endothelium derived cell line (ECV-304) from ATCC was used in this study. The PAI-1 mRNA expression and protein synthesis in the endothelial cells were detected by Northern blot and flow cytometry analysis, respectively. The activity of phospho-p44/p42 MAP kinase induced by TGFβ1 was determined by immunoprecipitation analysis and western blot. Results TGFβ1 rapidly increased PAI-1 mRNA expression in the endothelial cells, and this effect lasted at least 24 hours. The upregulation of PAI-1 mRNA expression induced by TGFβ1 in endothelial cells was inhibited by rhein in a dose-dependent manner. In addition, rhein inhibited endothelial PAI-1 protein production. Further study revealed that rhein had a significant inhibitory effect on the activity of phospho-p44/p42 MAP kinase induced by TGFβ1 in human endothelial cells. Conclusions Our results showed that rhein may have a protective effect on the endothelial dysfunction by inhibiting overexpression of PAI-1, indicating a way for the treatment of vascular diseases.