The goal of this study is to explore the efficacy and safety of Near-infrared light Photobiomodulation in patients with mild-moderate Alzheimer's disease(AD). This study will employ a randomized,blind,parallel controlled approach.Qualified subjects were selected and randomized (experimental group: control group=1:1). The subjects who entered the experimental group received 30 minutes of near-infrared light therapy once a day, 6 times a week, for 16 weeks of continuous treatment; The subjects who entered the control group received 30 minutes of non near-infrared light irradiation once a day (false treatment), 6 times a week, for 16 weeks.