Background: Uterine scar after cesarean section (CS) is an important cause of intrauterine adhesion, amenorrhea, uterine rupture, and infertility in females. Disruptions of angiogenesis play a critical role in the healing of uterine scars. In this study, we investigated the effects of human umbilical cord mesenchymal stem cells (hUC-MSCs) on angiogenesis regeneration in uterine scars in rats following full-thickness excision of uterine walls. Methods: Twenty rats that were not pregnant were categorized into the ‘normal’ group. Then, 100 pregnant rats were randomly assigned to four groups. In the natural group, rats underwent natural labor without any treatment. The CS group did not undergo any treatment after CS. In the PBS group, 0.5mL PBS was injected per uterine horn after CS. The hUC-MSC group had 5×10 6 hUC-MSCs injected per uterine horn after CS. Under sterile surgical conditions, rats were anesthetized with intraperitoneal injection of 3% pentobarbital sodium (45mg/kg). Approximately 2.0 cm was excised along the uterine wall in each uterine horn to establish a rat model of uterine scars. Hematoxylin and eosin (H&E) staining was applied to observe the tissue structure. Masson trichrome staining was used to reveal collagen deposition. Angiogenesis factors (FGF-2, VEGFA, and PDGFB) were detected via western blotting. The fate of transplanted hUC-MSCs was assessed using in vivo fluorescence imaging. The differential expression of microRNA and function prediction was detected using high-throughput sequencing. Results: hUC-MSCs significantly improved the morphology of the tissue structure and alleviated fibrosis in general on days 15, 30, and 60 of transplantation in the hUC-MSC groups. Moreover, the expressions of all three angiogenesis factors were increased at days 15 and 30 post-transplantation. In GFP analyses, although hUC-MSCs were observed on the uterine wall at days 15 and 30, those signals gradually weakened and then accumulated in other organs at day 60. In addition, miR-124-3p is higher in hUC-MSC groups. miR-124-3p targeted cell pathways of angiogenesis and the PI3K/AKT signaling pathway. Conclusion: hUC-MSC transplantation contributed to the repair of uterine scars, mainly through the suppression of excessive fibrosis and the enhancement of vascular remodeling.