To explore the efficacy and safety of near infrared light therapy for Alzheimer's disease. Each subject will be numbered and their medical records will be established. The subjects will be randomly assigned to the treatment group or the control group for 30 minutes/day (5-6 days a week) for 4 months while the treatment group is active settings and the control group is sham settings.Follow-up visits will be conducted at 2 months, 4 months and 2 months after treatment. At each follow-up, scale assessment, blood, MRI, and EEG were observed

Inclusion Criteria:

• The age of registration is 50-85 years old, male or female.
• The MMSE score < 26 points can be used to complete the scale assessment.
• Patients who are not on medication and who are taking psychotropic or cognitive-improving drugs must have a stable dose for at least 12 weeks before the trial and remain the same for the duration of treatment.
• Agree to participate in the clinical trial, willing to maintain the original treatment plan during the trial, and have signed the informed consent

Exclusion Criteria:

• MRI showed evidence of abnormalities other than Alzheimer's disease, such as cerebral infarction at key sites and severe leukodystrophy (Fezakas>Level 3).
• There are contraindications to MRI scanning, such as metal implants, claustrophobia, etc.
• A history of stroke or seizures.
• Photosensitive to sunlight or visible light, eczema or increased sensitivity of the skin at the treatment site.
• Severe vision or hearing impairment.
• Alcohol dependence, drug or other drug addiction or addiction tendency.
• During the study , subjects were pregnant, breastfeeding, or planning to pregnancy.
• He/She is currently participating in another study related to the treatment of AD.
• Researchers think that participants could not be included.