The free radical graft copolymerization of degraded starch and 3,5-dihydroxybenzoic acid was carried out with the horseradish peroxidase/H202 as the catalyst. A graft copolymer of starch and phenolic was prepared. The effect of temperature and pH on the enzymatic activity was discussed. And also it was investigated the graft conditions on the graft copolymerization. The structure and properties of the copolymer were characterized by Fourier Transform Infrared spectroscopy (FTIR), Nuclear Magnetic Resonance (HNMR) and gel permeation chromatography (GPC). The copolymer was used as tanning agent; applied results showed that it has excellent tanning properties.