Abstract: Abstact: Objective To observe the protection of Ducosahexaenoic acid（DHA）on primary culture cortical neurons exposed to amyloid beta protein 25-35. Methods The newborn Wistar rat cortical neurons were primarily cultured, then treated with DHA of different dose（20、50、100μmol/L） and aggregated Aβ25-35（25μmol/L）. CCK-8（Cell Counting Kit-8）staining was used to detect the survival rate of cortical neurons, and LSCM （laser-scanning confocal imaging system）was used to detect the changes of intracellular free calcium concentration in neurons labeled with the fluorescent dye Fluo-3/AM. Results 1）Compared with control group, the survival rate of cortical neurons was decreased in Aβgroup （31± 6 ％，n=8,　p＜0.05）, intracellular free calcium concentration in Aβgroup was elevated（249±12 ％，n=8, p＜0.05）; 2）incubation with DHA attenuated the decrease in the survival rate of cortical neurons and the increase in intracellular free calcium concentration induced by amyloid beta protein 25-35. Conclusions：1） Calcium overloading induced by amyloid beta protein 25-35 might be the main neurotoxicity effect ; 2）DHA could partly decrease calcium overloading induced by amyloid beta protein 25-35, which might be the important dmechanism of DHA attenuating the neurotoxicity effect.