The aim of this work is to numerically analyze the performance of a integrated power plant, which is composed of a biomass gasifier, a fuel cell and a gas turbine. The biomass gasifier is a steam fluidized bed system based on the UNIQUE concept. The chemical kinetics model is applied for the analysis of gas composition production, and the naphthalene is chosen as the tar composition. Effects of different moisture contents in the biomass and fuel utilization on the system performance are studied. The results show that, the biomass gasification-SOFC/MGT power plant can obtain an efficiency above 47% at the 200kW with the 20% of biomass steam content, which is higher than other biomass power plant. The increase of steam content in the biomass can decrease the system power and efficiency. The system power changes insignificantly with the increase of fuel utilization, while the system efficiency can increase significantly.