Inclusion Criteria:  age of 50-85 years old , either sex; met the diagnostic criteria for suspected AD; mild to moderate AD patients, that is, patients with 11 points ≤Mini-Mental State Examination(MMSE) total score ≤26 points total Hachinski ischemic scale (HIS) score ≤4 points; memory loss for at least 12 months, with a tendency of progressive deterioration; brain magnetic resonance imaging（MRI） scan suggesting a significant possibility of AD ; no obvious physical signs during nervous system examination; stable and reliable caregivers, elementary school or higher education level signed an informed consent form  Exclusion Criteria:  previous nervous system diseases (including stroke, optic neuromyelitis, Parkinson's disease, epilepsy, etc.); mental illness according to the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition（DSM-IV), Text Revision criteria, including schizophrenia and other mental illness, bipolar disorder, and severe depression or paralysis; unstable or severe heart, lung, liver, kidney, or hematopoietic diseases; uncorrectable visual and auditory disorders that affected completing neuropsychological tests and scale assessments; simultaneous use of cholinesterase inhibitors or memantine.