BACKGROUND CONTEXT Concentrate growth factor (CGF) is a third-generation platelet concentrate that releases a variety of bioactive substances and plays a good role in promoting tissue healing. Bone marrow mesenchymal stem cell (BMSCs) transplantation has been used to treat osteoporosis. However, effect of bone marrow mesenchymal stem cell combined with concentrate growth factor (CGF) on postmenopausal bone defects remains elusive. PURPOSE To observe the effect of BMSCs combined with concentrate growth factor (CGF) on postmenopausal bone defects and to explore related mechanisms. METHODS A total of 50 Sprague-Dawley rats were randomly divided into A (SHAM), B (model), C (CGF), D (BMSCs) and E (CGF + BMSCs) group. Group A did not remove ovaries and L6 vertebral body was created a 3mm × 3mm × 3mm large bone defect. The B, C, D, E groups experimented ovariectomy and then L6 vertebral body created a 3mm × 3mm × 3mm large bone defect model. C and E groups were filled with a suitable concentrate growth factor (CGF). D and E groups were injected Brdu-labeled BMSCs through tail vein. After 4 and 8 weeks of treatment, the vertebral body of the bone defect was taken for micro-CT and the parameters such as TV/BV, Tb.N, Tb.Th, Tb.Sp and vBMD. HE staining of vertebral bodies were to observe the morphology of bone tissue. Brdu immunohistochemistry and Brdu immunofluorescence were used to detect stem cell homing. Immunofluorescence was used to detect the expression of VEGF, BMP2 and NF-KB. Runx2, CTSK and VEGF NF-KB were detected by PCR and Western-bolt. RESULTS The Brdu labeling rate of BMSCs was up to 95.43%. After 4 and 8 weeks of intervention, bone formation in bone defects of groups C, D and E were significantly higher than that of group B. TV/BV, Tb.N, Tb.h and vBMD of C, D group were significantly higher than the model group, and the Tb.Sp of group B was higher than that of group C, D and E. The morphology of bone tissue in groups C, D and E was better than that in model group. The CGF combined BMSCs group showed a good synergistic effect, and their bone micro-structure and bone histomorphology were better than that of CGF or BMSCs alone. In the D and E groups, Brdu immunofluorescence and immunohistochemistry were detected in the bone defect. Compared with the model group, the expression of VEGF, BMP2 and NF-KB was more obvious in the bone defects of group C, D and E. Compared with the SHAM group, the expression of CTSK mRNA and protein in the model group was significantly up-regulated (P CONCLUSIONS BMSCs combined with CGF can effectively treat postmenopausal bone defects, which may promote bone defect repair by regulating inflammation, bone formation and angiogenesis. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.