【Abstract】 Objective To investigate the expression and the role of C3a-C3aR signaling pathway following SCIR in rat. Methods The SCIR model was established according to the Zivin's process with adult Sprague-Dawley (SD) rats weighed between 250 and 300 g. The rats were randomly divided into Sham-operated group (Sham group,n=9) , Ischemia group (I group, n=9) and Ischemia reperfusion group (IR group, n=36). According the time of reperfusion, the IR group was divided into IR12h group (n=9) , IR24h group (n=9) , IR48h group (n=9) and IR72h group(n=9). Etho- logical change was evaluated by the BBB 21-point open-field locomotor rating scale. ELISA was used to detect C3a content in serum. Immunofluorescence was performed to detect the expression and cellular localization of C3aR following SCIR in rat. Results Following SCIR, the rat motor behavior was significantly deficit. The C3a content of serum was elevated after SCIR in rat, peaked at 24h. C3aR significantly up-regulated in the lumbar spinal cord following SCIR. C3aR presents on the somas of motor neurons and the microglia located within spinal cord. Significant up-regulation of the C3aR was associated with increased numbers of C3aR-positive microglias. Conclusion This study suggested that C3a- C3aR signal pathway was activated in SCIR and C3a and may play an important role in promoting inflammatory and/or repair processes in the SCIR by regulating glial cell activation and chemotaxis.