The 20 MW/10 MW combined electricity generate system is studied which contents the biomass gasifier with the thermal power 60 MW/30 MW and the 660 MW coal fired boilers. In the negative-positive pressure single circulating fluidized bed gasification system, the circulating fluidized bed and fixed, bed system which tandem the two functions gasification and pyrogenic decomposition, the dual circulating fluidized bed combustion, gasification tandem bed system, specific analysis, argumentation and comparison are carried out from the engineering application and project demonstration perspective for the system's layout scheme. For variety of biomass fuel, ‘the positive pressure circulating fluidized bed gasifier and heat exchanger system’，and ‘the positive pressure circulating fluidized bed＋positive pressure fixed bed＋semi-coke back bed/straight row system’ are considered as alternative optimize scheme. After the implementation of the project, it will make important demonstration effect on the coupling of biomass gasification and coal combustion boilers.