Abstract: ［Objective］To observe the histological changes of bone microstructure of lumbar spine and femur in ovariectomized rats at different stages.［Methods］ Fifty 3-month-old female SD rats were randomly divided into two groups: ovariectomy group (OVX group) and sham operation group, with 25 rats in each group. The 5th lumbar vertebrae (L5) and femur of the two groups were taken out at 1 week, 4 weeks, 8 weeks, 12 weeks and 16 weeks after operation. The bone histomorphometric parameters were measured by microscopic image analysis software and SPSS 25.0 software for statistical analysis.［Results］ There were no significant changes in trabecular width, spacing between trabeculae and cortical bone thickness in L5 and femur in sham operation group (P > 0.05). In L5 vertebral body and OVX group, with the extension of castration time, the width of trabecular bone decreased (P < 0.05), and the spacing distance between trabeculae increased (P < 0.05); There was no significant change in cortical bone thickness (P > 0.05). Compared with the sham operation group in the same period, L5 in OVX group decreased significantly in trabecular width at 12 weeks after operation (P < 0.05), and the spacing between trabeculae increased significantly (P < 0.05); At 16 weeks after operation, the width of bone trabeculae decreased significantly (P < 0.05), and the spacing between bone trabeculae increased significantly (P < 0.05); There was no significant change in cortical bone thickness (P > 0.05). ［Conclusion］ After ovariectomy, there is obvious osteoporosis in the microstructure of lumbar spine and femur in rats, and the change of lumbar spine is earlier than that of femur, and the change of trabecular bone is earlier than that of cortical bone. Pathomorphometry has certain diagnostic significance.