The copolymer of phenol and acrylamide was synthesized by copolymerization using horseradish peroxidase (HRP)/H2O2 as catalyst. The effect of monomer composition on the copolymer tanning agent properties was investigated. The structure of the copolymer was characterized by Fourier transform infrared (FTIR) spectroscopy. The molecular weight was determined by gel permeation chromatography (GPC). The result shows that the average molecular weight of the copolymer is about 1900. Its molecule distribution index is much narrower. The copolymer was used as tanning agent, the result shows that the applied leather is excellent in softness and dyeing.