It is important to elucidate the interaction mechanisms between tannic acid （TA） and bovine serum albumin（BSA）/human serum albumin（HSA） for developing protein-based carriers of active components and exploring delivery mechanisms. Serum albumin （BSA/HSA） is a commonly used soluble protein-based carrier containing multiple hydrophobic cavities， which was binding sites of active components. The fluorescence quenching effect of BSA/HSA by TA under different conditions was studied by fluorescence emission spectroscopy， the quenching constants and thermodynamic parameters were calculated by mathematical equation to analyze the fluorescence quenching mechanism. Finally， the binding sites were determined by site Marker experiments and molecular docking technique. The results showed that fluorescence quenching of BSA/HSA by TA occur under different pH conditions， the quenching rate is highest at pH 7.4. The binding constants of TA and serum proteins obtained by nonlinear fitting are magnitude of 105-107 L/mol， which indicated that the binding ability is very strong and pH significantly affect the binding constants （P<0.05）， the binding constant is highest at pH 7.4. Thermodynamic parameters and molecular docking indicated that the binding of TA to BSA/HSA mainly through hydrogen bonding and hydrophobic interactions， site Marker experiments and molecular docking indicated that in pH 7.4， the binding sites are located in the hydrophobic cavity between domain IIA and domain IIIA， near the Sudlow's site I. The paper confirmed that the binding of TA to BSA/HSA is pH dependent， which provides a theoretical reference for the design and development of protein- TA carriers and provides meaningful guidance for TA applications.