【Abstract 】 Objective To investigate the effects of ginsenoside Rg1 on the expressions of SYN in Alzheimer’s disease of rat brain slices induced by okadaic acid (OA), and explore the mechanisms of gensenoside Rg1 in Alzheimer’s disease. Methods 400 μm thick brain slices which were cut from brains of 5weekold SD rats, were randomly divided into control group, sham group, lowdose ginsenoside Rg1 group, mediumdose ginsenoside Rg1 group and highdose ginsenoside Rg1 group, with 10 slices in each group. All these brain slices were cultured with artificial cerebrospinal fluid (ACSF). And brain slices in the ginsenoside R1 groups were administrated with the ginsenoside Rg1 (60, 120 and 240 μmol/L respectively) in ACSF. The concentration of OA in each group was 1 μmol/L. Expressions of SYN proteins in brain slices were determined by immunohistochemical method, and the results were analyzed by image acquisition and analysis system.Results The expression of SYN protein was decreased (P＜0.05) in the sham group, compared with the control group. The expression of SYN protein was increased (P＜0.05) in the ginsenoside Rg1 groups, compared with the sham group. Conclusion Ginsenoside Rg1 can increasing the expression of SYN in Alzheimer’s disease to protect the brain and slow down the aging process.