Objective: To explore the clinical efficacy of sodium oligomannate capsules combined with memantine hydrochloride and donepezil hydrochloride in the treatment of moderate Alzheimer’s disease (AD) and analyze its impact on cognitive function. Methods: Eighty patients with moderate AD admitted to the neurology outpatient clinic of our hospital from June 2021 to December 2022 were selected as the study subjects and randomly divided into a study group and a control group, each with 40 patients. The control group was treated with oral memantine hydrochloride and donepezil hydrochloride, while the study group was additionally treated with oral sodium oligomannate capsules for 24 weeks. The scores of neuropsychological scales [Montreal Cognitive Assessment (MoCA) and Mini-Mental State Examination (MMSE)], and Activities of Daily Living (ADL) scale were compared before and after treatment. Additionally, the levels of homocysteine (Hcy), central nervous system-specific protein (S100-β), interleukin (IL)-6, and tumor necrosis factor (TNF)-α were measured in both groups, and the treatment effects and adverse reactions were compared. Results: After 24 weeks of treatment, the MMSE, MoCA, and ADL scores of both groups were significantly higher than those before treatment (P < 0.05). Compared with the control group after 24 weeks of treatment, the study group had significantly higher MMSE, MoCA, and ADL scores (P < 0.05), and significantly lower levels of Hcy, IL-6, and TNF-α (P < 0.05). Both the study group and the control group showed reduced levels of Hcy, IL-6, and TNF-α after 24 weeks of treatment compared to before (P < 0.05), but there was no significant change in S100-β levels (P > 0.05). Conclusion: The combination of sodium oligomannate capsules, memantine hydrochloride, and donepezil hydrochloride is effective in the treatment of moderate AD. It can improve the cognitive function and daily living abilities of patients with dementia, enhancing their quality of life.