Abstract: The binding mechanism between gliadin and tannic acid was investigated by Fluorescence spectrophotometer,UV-visible spectrophotometer(UV-visible),and Fourier transform infrared(FTIR),and changes on structure and functional properties of wheat gliadin were also investigated. The results showed that the quenching type of wheat gliadin by tannic acid under noncovalent action was the static quenching of the compound,which was driven by hydrogen bond and combined with molar ratio 1:1. At the same time,tannic acid reacted with a free amino group on gliadin to form covalent conjugate under alkaline condition. In addition,the formation of the non-covalent mixture or covalent conjugate both caused the unfolding of gliadin. Furtherly,the formation of covalent conjugate resulted in higher effect on the gliadin secondary structure. The addition of tannic acid made the antioxidant capacity of the complex increase,and the non-covalent mixture exhibited higher antioxidant activity. Finally,gliadin-TA covalent conjugate increased the thermal stability of gliadin by 1.03℃,while the non-covalent mixture reduced the thermal stability of gliadin by 5.39℃.