Abstract: OBJECTIVE To investigate the effects of Rehmanniae-medicated serum on human glomerular mesangial cells (HRMC) stimulated with high concentration of glucose. METHODS Rehmanniae-medicated serum was prepared and analyzed for its serum components using LC-MS technology. MTT assay was used to detect the inhibitory rate of HRMC. Cell supernatant levels of SOD and MDA were measured by kits. ELISA assays were used to determine the contents of fibronectin and type IV collagen. Flow cytometry was used to analyze cell cycle distributions. Immunofluorescence was used to detect the expression of TGF-β₁ in HRMC. RESULTS Rehmanniae-medicated serum contains catalpa alcohol and stachyose. These active components could inhibit high level glucose-induced HRMC proliferation， reduced the production of extracellular matrix， and downregulated the mRNA expression of TGF-β₁. CONCLUSION Rehmanniae could inhibit ECM production by regulating TGF-β₁ so as to prevent the development of diabetic nephropathy.