Objective To study the change of ultrastructure of bone and the change of serum biochemical indexes after spinal cord injury (SCI). Whether the bones above and below the level of trauma are affected differently?To know well to what extent the secondary osteoporosis after SCI is. Method 110 Wistar rats 300-320 g weight ,4-5 months old were used. The control group only removed lamina with dura intact , without spinal cord injury at the level of the tenth thoracic vertebrae. The experiment group removed lamina , then , the SCI model of rats was made by the method of Allen's (60gcm). The experiment group's BBB (Basso, Beattie and Bresnahan ) score was 0 or 1 two weeks after operation. We observed the change of the serum concentration of calcium, phosphorus and alkaline phophatase (ALP) , the change of ultrastructure of osteocytes at the sites of tibial plateau and the surgical neck of the humerus. Results and Conclusion The bones above and below the level of trauma are both affected after SCI, but different extent of osteoporosis can be seen in different bones .The change of ultrastructure of osteocytes is remarkable when osteoporosis has happened.