Superoxide anion radical (O2 center dot-) is a noxious reactive oxygen species (ROS). Transition metal ion complexes have been generally used as antioxidants to eliminate ROS. In this work, the soybean protein isolate (SPI), a biodegradable vegetable protein, was first combined with polyvinyl alcohol through hydrogen bonding for the synthesis of SPI-based polymer microgel (SPI-PmG) carrier. Furthermore, a kind of novel water-soluble biopolymer/metal complex conjugate (SCM@SPI-PmG) was prepared by binding the 4-hydroxy salicylaldehyde amino acid Schiff-base metal complexes (HOSalCysM, M = Cu, Zn) with the SPI-PmG. The structure, morphology and stability of SPI-PmG were characterized by Fourier transform infrared spectroscopy, scanning electron microscope, X-ray diffraction pattern and thermogravimetric analysis. The result revealed that the diameter of the obtained SPI-PmG ranged from 150 to 400 nm. Besides, the scavenging superoxide anion free radical activity of biopolymer-metal complexes was determined by nitroblue tetrazolium light reduction assay method. Compared with the carrier SPI-PmG, the scavenging activity of the SCM@SPI-PmG was greatly improved. Remarkably, the superoxide dismutase (SOD) simulation of the SCCu@SPI-PmG reached 297.10%, and the SCZn@SPI-PmG simulation reached 35.13%. As a consequence, SCCu@SPI-PmG could be considered as a biofunctional mimic of enzyme SOD and has a promising application prospect in antioxidant drug field.