This paper presents a performance analysis for a Solid Oxide Fuel Cell (SOFC) - Micro Gas Turbine (MGT) hybrid power system using biogas. It was assumed that the supplied biogas consisted of CH4 and CO2; the performance was predicted comprehensively while the concentrations of both the components were varied. The concentration of CH4 in biogas was varied from 100% to 20%. The obtained results showed system performance degradation with decreasing CH4 concentration. It also suggested designing the cell active area to fulfil the requirements for an electrical capacity of 220 kW. It was found that lager cell active area was required while the CH4 concentration diluted. The results are promising for the future use of biogas in SOFC-MGT hybrid systems.