The invention discloses an affinity chromatography medium employing tetrapeptide as a functional ligand and a preparation method of the affinity chromatography medium. The method comprises the following steps: adding dry matrix and allyl bromide to a dimethyl sulfoxide solution, activating, and reacting activating matrix with N-bromo succinimide; enabling bromo alcoholized matrix to react with hexamethylendiamine to obtain amino activating matrix; sequentially washing with deionized water, absolute ethyl alcohol and anhydrous N,N-dimethyl formamide, adding an N,N-dimethyl formamide solution containing tetrapeptide, 2-(7-azobenzotriazole)-N,N,N',N'-te-tramethyluronium hexafluorophosphate and N,N-diisopropylethylamine, and coupling a tetrapeptide ligand; and putting a medium coupled to tetrapeptide in a mixed liquid of sodium acetate and acetic anhydride to obtain the affinity chromatography medium employing tetrapeptide as the functional ligand. According to the novel chromatography medium developed by the method, a functional group is tetrapeptide composed of tyrosine, phenylalanine, arginine and histidine, and is designed on the basis of a protein A binding site of an antibody Fc segment; the antibody binding selectivity is greatly improved; and the affinity chromatography medium can be applied to efficient separation of an antibody.