To observe the effects of polysaccharides in Ginseng Radix et Rhizoma Rubra on the behaviors and the levels of amyloid-beta 42(Aβ42)，superoxide dismutase(SOD)，malondialdehyde(MDA)，cyclic adenosine monophosphate(cAMP)，and acetylcholin esterase(AChE) in the brain issue of the Aβ42 transgenic Drosophila model of Alzheimer's disease，and explore the efficacy and mechanism of the polysaccharides in treating Alzheimer's disease.Methods:Wild-type(Canton-S) Drosophila was used as the blank group.Aβ42 transgenic Drosophila individuals were randomized into model，polysaccharides，and donepezil hydrochloride(positive control) groups.After 8 days，the climbing index，the number of fruit flies entering the barrier-free centrifuge tube，and the levels of Aβ1-42，SOD，MDA，cAMP，and AChE in the brain issue were compared.Results:The climbing index in the polysaccharides and positive control groups were higher than that in the model group(P<0.01)，while the index showed no significant difference between the polysaccharide group and the positive control group(P>0.05).In each time period，the number of fruit flies entering the barrier-free centrifuge tube in the polysaccharides and positive control groups was higher than that in the model group(P<0.05 or P<0.01).The polysaccharide and positive control groups had higher SOD activity and lower levels of Aβ1-42，MDA，cAMP，and AchE than the model group(P<0.01)，while there were no significant differences between the polysaccharides group and the positive control group(P>0.05).Conclusion:The polysaccharides in Ginseng Radix et Rhizoma RubraRed can increase the SOD activity and lower the Aβ1-42，MDA，cAMP，and AChE levels in the brain tissue of Drosophila.The polysaccharides may exert the therapeutic effect by inhibiting Aβ1-42 deposition，anti-oxidation，and improving nerve cell signal transduction，with the efficacy comparable to that of the positive control.