A cubic crystal form Co₃O₄ was synthesized using the sol-gel method and applied as catalyst in the visible light-driven photocatalytic degradation of 1,2,4-trichlorobenzene (1,2,,4-TCB). 1,2,4-TCB removal efficiency initially increased and was followed by a gentle decrease as the Co₃O₄ dosage increased, with the optimal dosage of 2.0 g/L. The degradation rate changed positively with light intensity and reaction temperature. However, pH exerted only a slight effect on 1,2,4-TCB degradation. Strong acidic and basic conditions were conducive to the photocatalytic degradation of 1,2,4-TCB. The optimal parameters for the photocatalytic degradation of 1,2,4-TCB were found at a Co₃O₄ dosage of 2.0 g/L, 350 W of illumination intensity, initial 1,2,4-TCB concentration of 7.5 mg/L at 30ºC, with 1,2,4-TCB removal efficiency of 90.13% after 6.0 hours photocatalytic degradation. The Co₃O₄ synthesized in the study with high-purity and stable properties guaranteed its high catalytic activity and stability. The possible mechanisms of visible light-driven photocatalytic degradation of 1,2,4-TCB with synthesized Co₃O₄ photocatalyst were also proposed.