Due to the increasing importance of environmentally friendly processes, the development of monomer synthesisand its polymerization using enzymes has been investigated throughout the world. In this paper, the polymerizationmechanism between silk fabrics and gallic acid (GA) in the presence of horseradish peroxidase (HRP) has been studied. Thepolymerization mechanism was studied in detail using UV-Vis and Fourier transform infrared spectroscopy (FT-IR), andhigh-performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI-MS) analysis. In addition,the dyeing properties and optimum reaction conditions were further investigated using the K/S values. The color fastness ofthe resulting silk fabrics has also been discussed. The results show that the dyeing mechanism for GA and silk fabric involvedlinking via the -NH2 and -OH groups in silk fiber and the -OH groups in GA. This was probably formed via the formation ofphenyl-phenyl, oxygen-phenyl, or amino-phenyl linkages. HRP significantly improved the dyeing properties of GA dyestoward silk fabrics. The optimum reaction conditions for dyeing silk fabrics have been proposed (Incubation period, 5 h;temperature, 50 oC; GA dosage, 10 mM; HRP, 6 U/ml, and H2O2, 5 mM). The color fastness of the resulting silk fabricsdisplayed high colorfastness in all the colorfastness tests performed.