Alzheimer's disease (AD), the most common cause of dementia, is characterized by cognitive impairment, mental and behavioural abnormalities, and social dysfunction. Current treatments can only delay the progression of AD, not cure it completely. In vitro studies have shown that Astragalus has toxic effects such as anti-hypoxia injury of nerve cells, anti-free radical damage, anti-excitatory amino acids, etc. It can be used to expand cerebral vessels, increase cerebral blood flow, improve cerebral microcirculation, protect brain cells, and repair damaged brain cells. However, the clinical effects of add-on Astragalus in improving cognition in these patients remain unclear. Therefore, this pragmatic clinical trial aims to determine the efficacy and safety of add-on Astragalus in improving cognition in patients with AD

Inclusion Criteria:

The inclusion criteria will be as follows:

1. Male or female aged ≥50 years and ≤85 years
2. Memory loss for at least 6 months, with a progressive worsening trend Patients with mild or moderate disease degree, that is, the total score of MMSE: 14 points < total score of MMSE <24 points, 0.5≤CDR≤2 points, and the total score of HAMD (24-item version) ≤20 points
3. Brain magnetic resonance imaging shows the degree of hippocampal atrophy is greater than or equal to grade 1
4. The modified Hachinski Ischemia Scale (m-HIS) score was < 4 points
5. The criteria described by the diagnostic and statistical manual of mental disorder-V for the diagnosis of dementia comply with the National Institute on Aging - Alzheimer's Association "Very likely AD" (National Institute of Aging-Alzheimer's Association, 2011).
6. There are no obvious positive signs in nervous system examination;
7. The subjects have the ability of reading, writing and communication, have a stable caregiver, accompany to attend the visit.
8. The basic treatment of AD before enrollment remained unchanged, and if long-term users needed to use it steadily for more than 4 weeks before randomization,the dose was kept as stable as possible during the study. Such drugs include: cholinesterase inhibitors.

Exclusion Criteria:

The exclusion criteria will be as follows:

1. MRI showed significant focal lesions, including one of the following: a. There were more than 2 infarcts with a diameter greater than 2cm; b. Infarcts in key areas such as the thalamus, hippocampus, entorhinal cortex, parorhinal cortex, angular gyrus, cortex, and other subcortical gray matter nuclei; c. White matter lesion Fazekas Scale ≥3
2. Patients who have taken other Chinese medicine preparations in the past three months
3. Allergy or contraindication of astragalus
4. There are other neurological diseases that can cause brain dysfunction or cognitive impairment; Mental and neurological retardation is present; Presence of malignant tumor
5. The modified Hachinski Ischemia Scale (m-HIS) score was ≥ 4 points. Patients who refuse or have MRI or EEG contraindications (pacemakers, coronary and peripheral arterial stents, Metal implants, claustrophobia, or severe visual or hearing impairment), refusing to draw blood
6. Pregnant or lactating patients;
7. Patients who have participated in other clinical studies within the past 3 months