Objective To investigate the protective effects of 13-methyltetradecanoic Acid(13-MTD) on focal cerebral ischemia in rats and the oxygen paradox of cultured astrocytes in vitro. Methods Almost pure astrocytes were obtained after Primary culture and subculture at the cerebral cortical of neonatal rats, and then the oxygen-glucose eprivasion 10h/reperfution 24h (OGD10h/R24h) model was made. 13-MTD 20, 40, 80mg/kg was administered immediately after reperfusion. Inverted Phase contrast microscope was used to observe the morphology of cells dynamically. MTT assay was employed to detect the mitochondrial reducibility, and Immunohistochemistry was used to measure the expressions of GFAP and AQP4 Proteins. Results After oxygen paradox, the pathological damage of the cerebral cortical astrocytes in neonatal rats was observed apparently, the mitochondrial reducibility was decreased significantly(P<0.01), the expression of AQP4 protein in AST was increased significantly(P<0.01). Compared with Vehicle, 13-MTD 20、40、80μg/ml can improve the above changes obviously (P<0.01), and it would be better by using 80mg/kg. Conclusions After OGD10h/R24h, the reducibility of astrocytes was decreased. The edema of astrocytes was significantly because of the expression of AQP4 Protein was up-regulated. 13-MTD 20、40、80μg/ml can imProve the above changes obviously and 13-MTD 80 μg/ml would be better. 13-MTD could protect astrocytes after OGD10h/R24h.