NiO/M -Al2O3 catalysts with different Ni contents were prepared by a two-step impregnation method and characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and transmission electron microscopy (TEM). Results showed that metallic Ni nanoparticles with diameters of 8-14 nm were formed and homogenously dispersed on the surface of the catalysts after reduction at 800 ℃. The catalysts were used for the catalytic conversion of toluene as a model tar compound in hot coke oven gas (COG) and showed excellent catalytic activity, stability and sulfur tolerance. Toluene could be fully converted and selectively hydrogenated to CH4 even using a low molar ratio of water to carbon (nH2O/nC=0.28) at 800 ℃ and under ambient pressure. The existence of H2O in the feed gas greatly enhanced the conversion of toluene and contributed to CH4 formation. Under similar conditions, naphthalene was converted into light fuel gases. Effects of H2 concentration and H2S in the feed gas were discussed. The Ni/M -Al2O3 catalyst was promising for the hydrocracking of tar compounds in hot coke oven gas with a low H2O content of 10%-15% (φ, volume fraction).