Background: Caveolin-1 (Cav-1) is known to regulate angiogenesis. However, little is known about Cav-1’s role in polycystic ovary syndrome (PCOS). This study aims to investigate Cav-1’s expression in the endometrium of PCOS rats during the implantation window and its association with endometrial angiogenesis. Methods: Female Sprague Dawley (SD) rats were randomly divided into the control and PCOS groups. The rats in the PCOS group mated after ovulation induction, while the rats in the control group mated during the estrus period. On the 2nd and 5th days of pregnancy, the rats were sacrificed, and the endometrium was isolated from their uteruses. Immunohistochemistry (IHC) staining of CD34 was used to evaluate the endometrial micro-vessel density (MVD). The expression of Cav-1 and vascular endothelial growth factor (VEGF) in the endometrium of both groups was assessed through IHC staining and real-time reverse transcription polymerase chain reaction (RT-PCR) analysis. Results: IHC analysis of endometrium tissue sections showed reduced MVD in PCOS rats on both the 2nd and 5th days of pregnancy. The endometrial expression of Cav-1 and VEGF were also significantly downregulated in the PCOS group compared to the control group during the implantation window. Interestingly, the endometrial expression of Cav-1 was positively correlated with MVD and VEGF. Conclusions: Our study demonstrated the decreased endometrial angiogenesis in PCOS rats during implantation window. This decrease was linked to decreased Cav-1 expression, suggesting Cav-1 is a potential therapeutic target for PCOS patients.