A series of Ni catalysts supported on La Ce O mixed oxides with different Ni content (Ce1-3xLa2xNixO2-?, x = 0.10; 0.20 and 0.25) prepared by combustion synthesis, was tested in tri-reforming reaction of simulated biogas. The influence of O2/CH4, CH4/CO2 molar ratios in the reaction stream has been evaluated caring out the reaction at 800 oC, under a fixed gas hourly space velocity (GHSV = 31,000 h-1). The highest catalytic activity was obtained with the Ce0.70La0.20Ni0.10O2-? sample that showed high stability (CH4, CO2 conversion rates and the H2/CO molar ratio in the reformed gas were 1.56 mmol/s gNi, 0.56 mmol/s gNi and 1.57, respectively) under an average biogas composition (CH4/CO2 = 1.5). No carbon deposition was detected after 150 h of reaction. The characterizations of the samples have highlighted that Ni and La ions were partially incorporated into CeO2 framework, cubic fluorite structure of CeO2 support was retained also at high level of doping. Ni metal phase in close contact with La2O3-CeO2 matrix coupled with Ni2+ with high cationic character appeared to be responsible of the catalytic activity and stability of the catalysts.