The present invention relates to a 2-amino-3-substituted mercaptopropionate derivative, a preparation method therefor and a use thereof. The 2-amino-3-substituted mercaptopropionate derivative according to the present invention has a structure as shown in formula (A). The present invention also comprises the use of the 2-amino-3-substituted mercaptopropionate derivative as a drug for treating and/or preventing neurodegenerative diseases, in particular Alzheimer's disease.