We investigated the effects of bone marrow-derived mesenchymal stem cells (MSCs) transplantation on the recovery of neurological functions in rat's MCAO (middle cerebral artery occlusion) model and its mechanism. MSCs were isolated from bone marrow of male Sprague Dawley (SD) rats. Female adult SD rats were randomly assigned into 4 groups: sham-operated group, MCAO group, vehicle group and MCAO + MSCs-treated group. MSCs were injected into the lateral ventricle of rats in the MSCs-treated group and the same volume of PBS was given to the vehicle group. The expressions of IL-10 and TNF-alpha were assayed by RT-PCR and ELISA detections at day 1 and 4 after MCAO. The infarction volume was measured by TTC-staining. All rats underwent behavioral tests before, as well as 1, 4, and 14 days after MCAO. MSCs significantly improved functional recovery compared with the control at day 14 after transplantation. Compared with the MCAO group and the vehicle group, the expression of IL-10 mRNA and its protein level in the MSCs group significantly upregulated. However, the expression of TNF-alpha at day 4 after MCAO in the MSCs group significantly decreased compared with that of the MCAO group and the vehicle group. As a result, transplantation with MSCs significantly decreased infarct volume at day 1 and 4. This study strongly suggested transplantation with MSCs could reduce neuronal injury post focal cerebral ischemia in rats partly by regulating the expressions of IL-10 and TNF-alpha in the brain.