Background: Alzheimer's disease (AD) is a degenerative disease of the central nervous system characterized by neuroinflammation and amyloid deposition. Folic acid (FA), a B vitamin, may improve the course of AD by modulating inflammation and neuroprotection. This study aimed to investigate the effects of FA supplementation on serum inflammatory cytokines (IL-1b, IL-6, TNF-a), amyloid (Ab1-42), Tau proteins, and neurotransmitters (GABA, 5-HT, Ach) in AD patients. Methods: We conducted a follow-up-controlled trial; 114 AD patients were included and randomly divided into a control group (donepezil treatment) and an experimental group (donepezil + FA treatment) for 3 months. Inflammatory factors, Ab1-42, Tau, neurotransmitter levels and nutritional status were assessed before and after treatment. Results: The total effective rate of the experimental group (89.47%) was significantly higher than that of the control group (75.44%), and the levels of inflammatory factors (IL-1b, IL-6, and TNF-a), Ab1-42, and Tau were significantly lower (P<0.05), and neurotransmitters (GABA, 5-HT, and Ach) and nutritional indexes (albumin and hemoglobin) were substantially higher. Conclusions: FA supplementation can effectively delay AD progression by inhibiting neuroinflammation, reducing amyloid deposition, regulating neurotransmitter metabolism and improving nutritional status.