In this study, an efficient and low-cost remediation technology was developed for organic contaminated soil. Using biochar and industrial iron powder as raw materials, an iron-carbon composite nanomaterial was prepared by industrial ball milling technology, which exhibited excellent reactivity to activate persulfate for the degradation of hydroxybiphenyl. The combination of high-resolution transmission electron microscopy and elemental scanning analysis showed that the particle size of iron-carbon composite material prepared by ball milling was 5-30 nm, with an average particle size of 15 nm, and the iron particles were evenly distributed in the carbon materials. When the dosage of iron-carbon composite nanomaterials of 0.10 g/L, and the concentration of sodium persulfate of 0.50 mmol/L, the removal efficiency of p-hydroxybiphenyl reached 100% within 120 min in aqueous solutions. In addition, the degradation rate of p-hydroxybiphenyl in soil can reach 85% under the same reaction conditions. Electron paramagnetic resonance (EPR) technique was used to elucidate the mechanism of persulfate activation, it was found that iron-carbon materials catalyzed the decomposition of persulfate to produce hydroxyl radical (·OH) and sulfate radical (SO₄·^-) with strong oxidation ability, which can rapidly degrade organic pollutants. The reaction system can degrade pollutants with a wide pH range and is not interfered by chloride ions and nitrates, which would provide a new technology for the remediation of organic contaminated soil.