The balance of mineralocorticoid receptor (MR) and glucocorticoid receptor (GR) is indispensable for maintaining the normal function and structure of the hippocampus. However, the changes of GR/MR and its effect on survival of hippocampal neurons after traumatic brain injury (TBI) are still unclear. Previous studies have indicated that high-dose glucocorticoids aggravate hippocampal neuronal damage after TBI. We hypothesize that the imbalance of GR/MR expression and activation caused by injury and irrational use of dexamethasone (DEX) aggravates posttraumatic hippocampal apoptosis and spatial memory dysfunction but that restoration by refilling MR and inhibiting GR promotes the survival of neurons. Using rat controlled cortical impact model, we examined the plasma corticosterone (CORT), corticosteroid receptor expression, apoptosis and cell loss in the hippocampus, and, accordingly, the spatial memory after TBI and GCs treatment within 7 days. Plasma CORT, MR and GR expression level were significantly reduced at 2 days after TBI. Accordingly, the number of apoptotic cells also peaked at 2 days. Compared with TBI control group, DEX treatment (5 mg/kg) significantly reduced plasma CORT, up-regulated GR expression, and increased the number of apoptotic cells and cell loss, whereas CORT replacement (0.3 mg/kg) up-regulated MR expression, inhibited apoptosis, and improved the spatial memory. The deleterious and protective effects of DEX and CORT were counteracted by spironolactone and mifepristone respectively. The results suggest that inhibition of GR by RU486 or the refilling of MR by CORT protects hippocampal neurons and alleviated spatial memory impairment via promoting GR/MR rebalancing after TBI.