Objective: To investigate the effects of tanshinone IIA on the alterations in morphology and the expression of transforming growth factor-β1 of peritoneal membranes in a rat model of peritoneal dialysis. Methods: Fifty male Sprague-Dawley (SD) rats were randomly divided into five groups (n=10 in each group). Intraperitoneal injection of 0.9% saline, standard lactate-buffered 4.25% glucose-based PDS, and standard lactate-buffered 4.25% glucose-based PDS with various concentrations of tanshinone IIA (50,100,200 mg/L) was performed for rats in each group once daily with an instillation volume of 20ml per injection for 30 days. Then, histological analyses, including hematoxylin and eosin (HE) staining and Masson staining, were carried out in parietal peritoneum. Immunohistochemistry were used to analyze the expression of transforming growth factor (TGF)-beta1. Results: As compared with control group, chronic high-glucose-based PDS exposure resulted in increased submesothelial compact zone thickness and accumulation of submesothelial matrix, as well as enhanced expression of TGF-β1 in parietal peritoneum. The peritoneal changes induced by PDS were significantly ameliorated by tanshinone IIA. Conclusion: Long-term exposure to high glucose-based PDS results in damages in peritoneal membranes and promotes the fibrosing process. Tanshinone IIA may be helpful in slowing the PDS-induced deterioration of peritoneal membrane.