The invention discloses a method for treating persistent halogenated hydrocarbons in soil by a slow-release compound remediation agent. The method includes steps: pre-ploughing contaminated soil, directly spreading a certain quantity of the slow-release compound remediation agent into ploughed soil, harrowing to well mix, watering to keep certain moisture content, and covering the soil surface with a protecting layer to realize anaerobic reduction dehalogenation reaction, wherein spreading quantity of the remediation agent is 0.05-1.5% of the dry weight of the contaminated soil, the soil ploughing depth is 25-40cm, the soil moisture content is adjusted to 50-80% of maximum field moisture capacity after spreading of the remediation agent, and remediation treatment time is 30-350d. The remediation method takes advantages of great adsorption performance of black charcoal, efficient chemical reducibility of nano zero-valence metal and dissimilatory iron reduction dehalogenation performanceof functional microorganisms to achieve physical, chemical and biological synergistic remediation effects on persistent halogenated hydrocarbon contaminated soil and has advantages of long action period, structural stability, low cost, environmental friendliness and the like.