Aim: To study the effect of rosiglitazone (RGZ) on expression and excretion of connective tissue growth factor (CTGF) in renal tissue and urinary of diabetic nephropathy rats. Methods: Three groups of rats were studied: normal control group(n = 8), STZ-induced diabetic model group(n = 8), diabetes RGZ-treatment group(n = 8). Urinary CTGF was measured at the 1st, 4th, 6th and 8th week, as well as the expressions of CTGF protein (by histochemical staining) at the 8th week by ELISA. Results: The urinary excretion rates of CTGF at 4thinverted commas6thinverted commas8th weeks and the expressions of CTGF protein in renal cortex at 8 th weeks significantly increased in STZ-induced model group compared with those in normal group (P < 0.01); RGZ-treatment decreased significantly the urinary excretion rates of CTGF and the expressions of CTGF protein in renal cortex compared with those in model group (P < 0.01). Conclusion: Rosiglitazone can suppress the expressions of CTGF protein in renal cortex, as well as the urinary excretion rates of CTGF in diabetic rats, which suggest that the renal protective effects of Rosiglitazone maybe partly due to its effects of down-regulating the CTGF production of renal tissue.