Background: Insulin resistance (IR) is one of the main pathophysiology of PCOS. Previous studies have shown that 4G/5G polymorphism in promoter region of plasminogen activator inhibitor-1 gene(PAI-1) can affect insulin sensitivity by elevating the level and activity of plasma PAI-1, involved in the formation of IR. In order to elucidate the relationship between 4G/5G polymorphism of PAI-1 gene and PCOS, we used transmission disequilibrium test (TDT) to study the nuclear family of PCOS. Purpose: This study used family-based analysis of TDT to determine whether an association exists between 4G/5G polymorphism of PAI-1 gene and PCOS and in Han Chinese in order to identify PAI-1 gene as a genetic susceptibility factor for PCOS. Methods: Eight hundred and fifty-five participants consisting of 285 trios (mother, father and offspring with PCOS) were recruited from the Center for Reproductive Medicine, Shandong University, from July 2007 to August 2014. 4G/5G polymorphism of PAI-1 gene was genotyped using direct sequencing protocol and TDT was used to analyze the association between PAI-1 gene and PCOS. Results: Though the 5G allele in PAI-1 gene was overtransmitted in families, no statistical significance existed and there was no association between PAI-1 gene and PCOS. The levels of FINS, HOMA-IR and TG were significantly different between obese and lean PCOS and the parents.Conclusion: No significant evidence of association or linkage was found between 4G/5G polymorphism of PAI-1 gene and PCOS, indicating that PAI-1 gene was unlikely to play a major role in the etiology of PCOS in our sample.