The invention provides 3-amino-3-arylpropionic acid with the structure shown in the formula I in the specification, wherein R1 is substituted or non-substituted phenyl, substituted or non-substituted bicyclo or tricycloaryl or substituted or non-substituted monocyclo, bicyclo or tricycloaryl containing at least an N, O or S atom. The invention also provides a preparation method of 3-amino-3-arylpropionic acid. The unnatural amino acid 3-amino-3-arylpropionic acid can synthesize a series of polypeptide compounds with other amino acids. The polypeptide compounds have certain inhibitory activity against histone deacetylase (HDAC), are possibly used for preventing or treating diabetes, diabetes complications, acute promyelocytic leukemia (APL), inflammatory diseases, organ transplantation rejection, protozoan infection, autoimmune diseases or tumors, etc and have certain medicinal value. The preparation method has the beneficial effects of easily-obtained raw materials, simpleness, convenient operation and higher yield.