As a clean renewable energy, biomass energy is now gradually being used in electric power, chemicals, heating and other related industries with great potential, and further research is also ongoing in depth. At the same time, because the demand of the construction of environment-friendly society, feed gas from biomass gasification for Fischer-Tropsch fuel synthesis in this way also has gained more and more attention. For the selection of ideal way to obtain synthetic fuels with relatively high system efficiency from biomass, this paper simulation for a variety of processes and different gasification conditions based on Gibbs free energy minimization method. The impacts of pre-treatment of biomass, temperature of gasification and pressure are analyzed. In the evaluation of energy efficiency of the system, an exergy analysis of biomass integrated process is presented. All parts of the process were calculated and compared, which mainly includes the gasification, pre-treatment, HRSG, compression, purification, WGS and FT reactor sections. The results showed that in the process the largest exergy losses take place in the gasifier section, and the pre-treatment of biomass materials for this part will have a greater impact on exergy loss.