Poly(ethylenimine) (PEI) as a long flexible chain has been well used in protein chromatography with the advantages of high spatial utilization and "chain delivery" effect. In this work, two resins, i.e., poly(ethylenimine)-4FF resin (PEI-4FF resin) and Ac-YFRH-PEI-4FF resin by grafting tetrapeptide to PEI-4FF resin, were prepared for the protein adsorption and chromatographic separation. The pH-dependent adsorption properties of PEI-4FF resin and Ac-YFRH-PEI-4FF resin were discovered by getting the data of adsorption capacities of bovine serum albumin (BSA) and immunoglobulin G (IgG) under different pH conditions and buffer systems. The results showed high binding capacities of BSA on PEI-4FF resins across a range of pH values (5.0-8.9) with almost very little adsorption of IgG over a pH range from 5.0 to 8.0, indicating that IgG could be separated by flow-through method using PEI-4FF resin. Since PEI has the advantage of having many flexible branched chains and Ac-YFRH (Ac-Try-Phe-Arg-His) as a peptide ligand has the advantages of comparatively high stability and low immunogenicity for antibody adsorption, Ac-YFRH-PEI-4FF resins were prepared by using PEI as the spacer arm and Ac-YFRH as the peptide ligand. The isotherm adsorption of the Ac-YFRH-PEI-4FF resin showed that the maximum binding capacity of IgG (q(m) = 123.6 mg/g resin, K-d = 0.10 mg/mL) was far more than that of BSA (q(m) = 62.0 mg/g resin, K-d = 0.25 mg/mL) at pH 8.0. Meanwhile, this tetrapeptide resin also showed high binding capacity of BSA (q,, = 131.0 mg/g resin, K-d = 0.05 mg/mL) and low binding capacity of IgG (q(m) = 2.0 mg/g resin, K-d = 0.01 mg/mL) at pH 5.0, indicating that the separation of BSA and IgG could be achieved with the big differences in adsorption behaviors.