To study the degradation of hexachlorobenzene (HCB) in contaminated soil by dielectric barrier discharge (DBD), a fluidized-bed DBD reactor was used to degrade HCB in contaminated soil. The results showed that a discharge current pulse could be generated with a 20 μs pulse width. When the air flow rate was 4.0 L/min, the soil reached a fully fluidized state. The energy density of reactor increased with the increase of discharge voltage, which promoted HCB degradation, but increasing heating led to lower energy utilization. The HCB degradation rate reached 97.3% after 32 min while the energy density was 172.5 J/L at a discharge voltage of 16 kV. The neutral or alkaline condition was more beneficial to HCB degradation than the acidic condition. With the increase in the initial HCB concentration, the degradation rate of HCB decreased, but the absolute degradation amount increased. The degradation of HCB conformed to first-order kinetic equation. During the discharge process, the C—Cl bond was attacked by active substances, and low-substituted chlorobenzene and small molecular organic acids and other byproducts were generated, which indicated that the degradation of HCB in contaminated soil was mainly a dechlorination process. The research results have important practical significance for the remediation of actual contaminated soil.