Through the sulfonation of protocatechuic acid, sodium 5-carboxy-2,3dihydroxybenzenesulfonate (SPA) was synthesized. The structure of the sulfonated derivative was confirmed by FT-IR, MS, H-1 NMR, C-13 NMR, single crystal X-ray diffraction, and thermogravimetric analysis. The antioxidative activities of the derivative SPA were evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging method and reducing power determination, showing that SPA had strong antioxidative effects. Meanwhile DPPH scavenging progress by SPA was analyzed from dynamics experiments. Isothermal titration calorimetry (ITC) and circular dichroism (CD) were applied to investigate the interaction between the derivative SPA and human serum albumin (HSA).