Chlorinated phenols are a kind of environmental priority pollutants that attract much attention. The effect of Ni on the removal of pentachlorophenol( PCP) with Fe nanoparticles was investigated in this study. Fe nanoparticles and Ni submicron particles were synthesized using chemical reduction method and wet chemical techniques,respectively. And the concentrations of PCP and chloride ion in solutions were measured with and without Ni present. The results showed that the dechlorination of PCP was promoted in the presence of Ni particles,and the dechlorination efficiency was reduced along with the increase of Ni size. When the diameter of Ni particle was smaller than 300 nm,the removal efficiency of PCP was obviously increased in the initial 4 h,and then became the similar to that of the system with Fe only. When the diameter of Ni particle was between 400 nm and 1 μm,the removal efficiency of PCP was increased in the initial 1 h. Then the removal of PCP was inhibited,and the inhibition was increased with the increase of Ni size. Later,the removal efficiency was the similar in various systems.