Abstract: The preparation and characterization of the affinity-ligand-modified liposomes were studied. The optimum conditions for liposome preparation and the ligand-modifying reactions were determined. Using p-aminobenzamidine (PAB) as an affinity ligand, the trypsin inhibition kinetics by PAB-modified liposomes and the characteristics of affinity ultrafiltration of trypsin were investigated. The results showed that the equilibrium binding constant of the PAB-modified liposomes for trypsin was more than 1/4 of that of free PAB for trypsin and the affinity-ligand-modified liposomes were effective in affinity separation for trypsin.