Objective： To investigate the effects of secreted protein acidic and rich in cysteine （SPARC） peptide on ultramicrostructure and extracellular matrix secretion of human mesangial cells cultured in vitro. Methods： Human mesangial cells （HMC） were incubated at the presence of SPARC peptide （50μg/ml） for 48 h and 96 h separately; HMC cultured without SPARC peptide was taken as control. The cell ultramicrostructure was observed by transmission electron microscope. Real-time fluorescent quantitative PCR （RT-PCR） was used to detect mRNA levels of collagen typeⅠ （ColⅠ ）, collagen type Ⅳ （ColⅣ）, fibronectin （FN）, and laminin （LN） 96 hours after culture, and the results were compared between the 2 groups. The secreted levels of ColⅠ , ColⅣ, FN, and LN protein were measured and compared by enzyme-linked immunosorbent assay （ELISA） in the 2 groups. Results： There was no obvious change in HMC in the control group. After cultured for 48 hours, a few HMC in experimental group showed initial appearance of apoptosis; after cultured for 96 h, a great number of HMC had a typical apoptotic appearance and there were typical apoptotic bodies under electron microscope. RT-PCR showed that, compared with the control group, the experimental group had significantly decreased levels of ColⅠ , ColⅣ and FN mRNA （P〈0.05, P〈0. 01） ; ELISA results showed that the secretions of ColⅠ , ColⅣ, and FN protein in the experimental group were greatly lower than those in the control garoup （P〈0.05, P〈0.01）. Conclusion： SPARC peptide can effectively induce apoptosis of human mesangial cells and down regulate the secretion of extracellular matrix in vitro