Abstract: In order to investigate the synergistic effects between the components of Coix lacryma-jobi protein (CP), we used catechin (CC) and CP as the raw materials, and introduced different concentrations of catechin to the CP to prepare a catechin-Coix lacryma-jobi protein intercrops (CC-CPs). Fourier transform infrared spectroscopy (FTIR), fluorescence spectroscopy, and SDS-PAGE were used to examine the structural attributes of the CC-CP intercrops, as well as their DPPH radical scavenging and reducing capacities. The results revealed that CC applied at different concentrations interacted with CP, resulting in structural alterations and a notable increase in the disulfide bond content of the CC-CP treated groups. Additionally, compared with the control group in which CP was unmodified, there was a significant reduction in surface hydrophobicity (P<0.05), and in FTIR spectra, we detected notable reductions in the intensities of the peaks corresponding to the amide I (1600~1700 cm⁻¹) and amide II (1500~1600 cm⁻¹) bands. Furthermore, the addition of CC resulted in alterations in the particle size and net charge number of Coix lacryma-jobi protein (CP), with the size of particles showing a tendency of an initial increase and subsequent reduction in response to an increase in the concentration of CC, whereas the absolute value of the reciprocal zeta potential was found to be largest at a CC concentration of 60 μmol/g protein. Moreover, the introduction of CC was observed to have a pronounced effect on CAU proteins, resulting in a significant blue shift in the λ_max (wavelength) of CC-CP intercrops. The results of our analysis of in vitro antioxidant activity revealed that compared with CC, the CC-CP intercrops were characterized by a higher degree of synergistic antioxidant activity, with scavenging rates of 75.58% and 66.65% for ABTS⁺ and ·OH radicals, respectively. Collectively, our findings in this study indicate, the combination of CC and CP can result in a greater effect than the sum of the parts. These findings may provide a theoretical basis for the moderate processing of Coix lacryma-jobi protein. Furthermore, the rational design of protein intercrops and supplements may facilitate the development of new functional constituents that can be applied to produce more nutritious, sustainable, and healthier foods.