A randomized controlled clinical study will be conducted in Xuanwu Hospital of Capital Medical University. This study initially explore the effect of selective vagus nerve(C fiber) stimulation on mild-to-moderate AD patients, in order to regulate the activity of the locus coeruleus-norepinephrine network, and to observe the improvement of cognitive function and memory function. We aim to evaluate the efficacy and safety of minimally invasive selective vagus nerve stimulation in the treatment of mild-to-moderate AD patients, to clarify the effective mechanism, and to provide an effective clinical treatment strategy.