Background: Polycystic ovary syndrome (PCOS) is a complex and heterogeneous endocrine disorder that has many characteristic features including hyperandrogenemia, insulin resistance and obesity. The beneficial effects of metformin on reproduction, metabolism and endocrine, especially with the capacity to ameliorate insulin resistance (IR) in polycystic ovary syndrome (PCOS), place it as a good alternative for its widely prescribed, but its association with PCOS offspring remains uncertain. We aim to investigate the impact of metformin on reproductive, endocrine and metabolic characteristics in female offspring born to letrozole-induced PCOS-IR rats.Methods: 45 female wistar rats were implanted with letrozole-continuous-release pellets or placebo, subsequently treated with metformin or vehicle control, then mated with healthy male wistar rats. Estrous cycle, endocrine hormone profile, fasting insulin measurements and glucose tolerance test have been investigated and the expression of INSR in pancreas, FSHR and LHCGR in ovaries have been analyzed with Quantitative Real-time Polymerase Chain Reaction and Western Blotting assay.Results: Decreased conception rate and increased multiple pregnancy rates were found in PCOS-IR rats, which significantly improved after metformin treatment. Metformin significantly decreased the risk of body weight gain and increased INSR expression of pancreas in female F1 offspring in PCOS-IR rats. Decreased FSHR and increased LHCGR expressions in ovary were observed in female F1 rats of PCOS-IR and PCOS-IR+Met group. Nevertheless, there were no significant differences of INSR, FSHR and LHCGR expressions in female F2 offspring of PCOS-IR rats, as well as other PCOS phenotypes.Conclusions: The current study indicates that widespread reproductive, endocrine and metabolic changes in letrozole induced PCOS-IR rat model, but those PCOS phenotypes could not be inherit to offspring generations stably. Metformin may contribute to improve obesity, hyperinsulinemia and insulin resistance of female F1 offspring in PCOS-IR. The results of this study can be used as a theoretical basis for supporting metformin-using in the treatment of PCOS-IR patients.