Objective To study the therapeutic effect and mechanism of geraniin on experimental osteoporotic fracture(OPF)in rabbits.Methods Rabbits were randomly divided into sham operation group,model group,different doses of geraniin groups(20,10,5 mg/kg)and simvastatin group(5 mg/kg).OPF model of rabbits was constructed by ovariectomy and bone defect in the middle radius.The changes of bone mineral density in rabbits were detected by bone densitometer.X-ray imaging and Micro CT were used to detect the healing of osteoporotic fractures in rabbits.Bone biomechanical changes were detected by bone strength instrument.The pathological changes of bone tissue were detected by HE staining.Automatic biochemical analyzer and Elisa were used to detect the changes of serum bone turnover biochemical markers and calcium salt and phosphorus salt content in ash composition.Results Geraniin significantly increased the bone mineral density of femur,spine and the whole body of OPF rabbits(P＜0.01),improved the patency of bone marrow cavity and the continuity of bone cortex,increased the bone volume/total volume of OPF rabbits,reduced the bone surface area/bone volume,improved the integrity of trabecular structure,increased the number of trabecular bone and the thickness of trabecular bone,and reduced the spacing of trabecular bone.In addition,geraniin improved biomechanical indexes such as maximum load,structural stiffness and maximum displacement of OPF rabbits,and improved bone microstructure.In addition,geraniin significantly increased the levels of calcium(Ca2+)and phosphorus(P)in serum of OPF rabbits,decreased the levels of alkaline phosphatase(ALP),tartrate-resistant acid phosphatase(TRACP),type I collagen cross-linked carboxyl terminal peptide(CTX-1)and urinary deoxypyridinoline(DPD)(P＜0.01),and increased the contents of calcium and phosphorus in bone ash(P＜0.01).Conclusion Geraniin can effectively promote the healing of osteoporotic fractures and improve bone microstructure and biomechanical properties.The mechanism may be related to the increase of bone mineral content and the regulation of bone metabolism.