The present invention relates to a composition comprising an extract of Dioscorea opposita having neuron-protective activity for preventing and treating brain disease. The extracts from Dioscorea opposita show potent neuronal cell protective activity by inhibiting neuronal cell death caused by neuro-toxicity of glutamate and H.sub.2O.sub.2 therefore it can be used as the therapeutics or health food for treating and preventing brain diseases.