Objective： To explore the effects of thiazolidinediones（TZDs） pioglitazone on proliferation and differentiation of human preadipocytes. Methods：Omental adipose tissue biopsies were obtained from 15 patients who were undergoing elective open-abdominal surgery. The primary culture and differentiated induction of human preadipocytes were performed, and the human preadipo-cytes were treated with pioglitazone at different concentrations at proper moments. Dynamic morphological changes of the human preadipocytes were observed, and their proliferation and differentiation were assessed with Colorimetric MTT Assay and Oil Red O Staining. Results：After 24 hours and 72 hours with pioglitazone, 0.1 μmol/L（μmol／ml） pioglitazone increased the MTT values of the human preadipocytes by 25.3% and 34.8%，respectively（P < 0.05）, while 1 μmol/L pioglitazone by 27.4% and 26.6%（P < 0.05), compared with the control group without pioglitazone. The human preadipocytes with pioglitazone cumulated more adipose in the endochylema than those without pioglitazone obviously. 0.1 μmol/L pioglitazone increased the differentiation degree of the human preadipocytes differentiated for 8-10 days by 44.81% and 1 μmol/L pioglitazone by 53.76%（P < 0.05）. Conclusion：Thiazolidinediones pioglitazone may significantly promote the proliferation and differentiation of the human omental preadipocytes.