The paper mainly investigated the hexachlorobenzene (HCB) removal capability from water by nano zero valent iron/activated carbon and factors that affect removal capability. Results revealed that HCB removal fit Langmuir model well indicating chemical sorption. Monitoring of HCB and its potential dechlorination products confirmed that HCB removal include both adsorption and dechlorination. Solution pH and co-present anions and cations both affected HCB removal. HCB removal was favored at acidic pH since zero-valent iron oxidation was facilitated while pH was low. Bicarbonate, chloride and sulfate at low concentration could improve HCB removal through corrosion facilitation while the effect leveled off at high concentration. In contrast, nitrate competed with HCB for zero-valent iron can result in inhibition. HCB removal decreased with the increase of nitrate concentration. Cation such as magnesium has no effect on removal. However, presence of copper and ferrous enhanced removal by changing the solution pH and zero-valent iron's redox characteristics.