Abstract: A Ni-dolomite catalyst with promoter Lanthanum was prepared by kneading method. The catalyst was used for the cracking reaction of tar model compound containing N-dodecane, cyclohexane, toluene and methylnaphthalene in an atmospheric fixed reactor. The effects of temperature, space velocity and the ratio of water and ingredient on the yield of gas products were examined. The stability test and reaction-regeneration experiments were conducted. Moreover, cracking characteristics of dust-containing tar over the catalyst and dust deposition mechanism were investigated. The results show that the optimum operating condition for the catalyst is reaction temperature 800℃, space velocity 300h^-1, the ratio of water to ingredient 5:1. The optimum regeneration condition is 700℃ and 1h. XRD results show that MgO-NiO solid solution and La(NiO₃) crystalline phase are converted in the modified dolomite catalyst. Different dust species depositing on the catalyst surface have different influences on the catalytic activity. CaO can improve the catalytic activity. The deposition of Fe₂O₃ can convert into a new crystalline phase NiFe₂O₄. SiO₂ plays a promoting role in carbon deposition, which can significantly inhibit the catalytic activity.