Objective: To perform intrauterine adhesion modeling, and to investigate the repair effect of hypoxic treated bone marrow mesenchymal stem cells (BMSC) and their derived exosomes (BMSC-exo) on endometrial injury. Methods: BMSC and their exosomes BMSC-exo extracted from rats' femur were cultured under conventional oxygen condition (21%O2) or hypoxia condition (1%O2). Intrauterine adhesion modeling was performed on 40 healthy female SD rats by intrauterine injection of bacterial lipopolysaccharide after curettage. On the 28th day of modeling, 40 rat models were randomly divided into five groups, and interventions were performed: (1) NC group: 0.2 ml phosphate buffered solution was injected into each uterine cavity; (2) BMSC group: 0.2 ml BMSC (1×106/ml) with conventional oxygen culture was injected intrauterine; (3) L-BMSC group: 0.2 ml of hypoxic cultured BMSC (1×106/ml) was injected intrauterine; (4) BMSC-exo group: 0.2 ml of BMSC-exo cultured with conventional oxygen at a concentration of 500 μg/ml was injected into the uterine cavity; (5) L-BMSC-exo group: 0.2 ml hypoxic cultured BMSC-exo (500 μg/ml) was injected intrauterine. On the 14th and 28th day of treatment, four rats in each group were sacrificed by cervical dislocation after anesthesia, and endometrial tissues were collected. Then HE and Masson staining were used to observe and calculate the number of glands and fibrosis area in the endometrium. The expressions of angiogenesis related cytokines [vascular endothelial growth factor A (VEGFA) and CD31], and fibrosis-related proteins [collagen-Ⅰ, collagen-Ⅲ, smooth muscle actin α (α-SMA), and transforming growth factor β1 (TGF-β1)] in endometrial tissues were detected by western blot. Results: (1) HE and Masson staining showed that the number of endometrial glands in L-BMSC group, BMSC-exo group and L-BMSC-exo group increased and the fibrosis area decreased compared with NC group on the 14th and 28th day of treatment (all P<0.05). Noteworthily, the changes of L-BMSC-exo group were more significant than those of BMSC-exo group (all P<0.05), and the changes of BMSC-exo group were greater than those of BMSC group (all P<0.05). (2) Western blot analysis showed that, compared with NC group, the expressions of collagen-Ⅲ and TGF-β1 in BMSC group, L-BMSC group, BMSC-exo group and L-BMSC-exo group decreased on the 14th and 28th day of treatment (all P<0.05). As the treatment time went on, the expressions of fibrosis-related proteins were different. Compared with BMSC group, the expressions of collagen-Ⅲ, α-SMA and TGF-β1 in the BMSC-exo group and L-BMSC group decreased on the 28th day (all P<0.05). Moreover, the expressions of collagen-Ⅲ and TGF-β1 in L-BMSC-exo group were lower than those in BMSC-exo group on the 28th day (all P<0.05). And the expressions of collagen-Ⅰ, α-SMA and TGF-β1 in L-BMSC-exo group were lower than those in L-BMSC group on the 28th day (all P<0.05). (3) The results of western blot analysis of VEGFA and CD31 showed that, the expressions of VEGFA and CD31 in BMSC group, L-BMSC group, BMSC-exo group and L-BMSC-exo group increased on the 14th and 28th day of treatment compared with NC group (all P<0.05). Treatment for 28 days, the expressions of VEGFA and CD31 in BMSC-exo group and CD31 in L-BMSC group were higher than those in BMSC group (all P<0.05). Moreover, the expressions of VEGFA and CD31 in L-BMSC-exo group were higher than those in BMSC-exo group and L-BMSC group on the 28th day (all P<0.05). Conclusions: Treatment of BMSC and their exosomes BMSC-exo with hypoxia could promote endometrial gland hyperplasia, inhibit tissue fibrosis, and further repair the damaged endometrium in rats with intrauterine adhesion. Importantly, hypoxic treatment of BMSC-exo is the most effective in intrauterine adhesion rats.