Conversion of biomass or steam gasification to synthesis gas and hydrogen contributes to the environmental protection. This is because the synthesis gas can be considered to be a promising energy carrier in the future. Thus develop catalysts for the steam gasification and tar reforming have been more interesting. The formation of nickel catalyst and lanthanum - magnesium promoter layers on alumina support were carried out by sequential impregnation method. After each impregnation steps, catalysts powders were calcined at 650, 750, 850oC for 2 and 5 hours. The metal oxides impregnation improved surface area by 2-2.5 times and also enlarged particle size of catalysts. The overall particle sizes and the specific surface area of developed catalysts were in the range of 13.93-28.00 μm and 11.34 – 18.70 m2/g. The 5%La2O3-5%MgO-10%Ni/Al2O3 catalyst calcined at 650°C for 2 hours had largest particle size and highest specific surface area of 28.00 μm and 18.70 m2/g, respectively. The surface area of catalyst was decreased with the increase calcination temperature and soaking time. Main phases of Al2O3 corundum and other diffraction lines corresponding to La(AlO3), MgO and/or NiO and/or MgNiO2 and Ni were detected. Stronger degree of interaction between La promoter and alumina support was found as calcination temperature and time increased. All catalyst appeared in a fairly uniform macroscopical distribution of the element.