The use of solar photocatalytic degradation of pollutants is one of the most promising technologies to solve water pollution problems and achieve solar energy conversion. By changing the amount of g-C₃N₄ added, g-C₃N₄/Co₃O₄ catalysts with different g-C₃N₄ mass fractions are prepared based on the calcination method with cobalt nitrate hexahydrate (Co（NO₃)₂-6H₂O) and urea (NH₄CNO) as raw materials. The samples are analyzed and characterized using X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS） and ultraviolet visible absorption spectroscopy （UV-vis DRS）. To speculate on the active species of the catalyst, capture agent experiments are conducted on it. The results indicate that the synergistic effect between g-C₃N₄ and Co₃O₄ can improve the transfer and separation efficiency of charge carriers at the interface between the two phases. Under visible light, the degradation effect of 10% g-C₃N₄/Co₃O₄ is the best, with a degradation rate of 66.50%, which is higher than the degradation effect of single Co₃O₄ （degradation rate of 35.90%）. The active species of the catalyst are mainly superoxide radicals（·O₂-） and holes（h⁺）. After compounding with g-C₃N₄, the drawbacks of Co₃O₄ electron hole pair, such as too fast recombination and a deficient energy level structure, are improved, providing ideas for the degradation of organic pollutants in the future.