Dexamethasone has been widely used after various neurosurgical procedures due to its anti-inflammatory property and the abilities to restore vascular permeability, inhibit free radicals, and reduce cerebrospinal fluid production. According to the latest guidelines for the treatment of traumatic brain injury in the United States, high-dose glucocorticoids cause neurological damage. To investigate the reason why high-dose glucocorticoids after traumatic brain injury exhibit harmful effect, rat controlled cortical impact models of traumatic brain injury were established. At 1 hour and 2 days after surgery, rat models were intraperitoneally administered dexamethasone 10 mg/kg. The results revealed that 31 proteins were significantly upregulated and 12 proteins were significantly downregulated in rat models of traumatic brain injury after dexamethasone treatment. The Ingenuity Pathway Analysis results showed that differentially expressed proteins were enriched in the mitochondrial dysfunction pathway and synaptogenesis signaling pathway. Western blot analysis and immunohistochemistry results showed that Ndufv2, Maob and Gria3 expression and positive cell count in the dexamethasone-treated group were significantly greater than those in the model group. These findings suggest that dexamethasone may promote a compensatory increase in complex I subunits (Ndufs2 and Ndufv2), increase the expression of mitochondrial enzyme Maob, and upregulate synaptic-transmission-related protein Gria3. These changes may be caused by nerve injury after traumatic brain injury treatment by dexamethasone. The study was approved by Institutional Ethics Committee of Beijing Neurosurgical Institute (approval No. 201802001) on June 6, 2018.