The coal and biomass coupling power generation technology is considered as a promising technology for energy conservation and emission reduction.In this paper,a novel coal and biomass indirect coupling system is proposed based on the technology of biomass gasification and co-combustion of coal and gasification gas.For the sake of comparison,a coal and biomass direct coupling system is also introduced based on the technology of cocombustion of coal and biomass.The process of the direct and the indirect coupling system is simulated.The thermodynamic and economic performances of two systems are analyzed and compared.The simulation indicates that the thermodynamic performance of the indirect coupling system is slightly worse,but the economic performance is better than that of the direct coupling system.When the blending ratio of biomass is 20%,the energy and exergy efficiencies of the indirect coupling system are 42.70% and 41.14%,the internal rate of return (IRR) and discounted payback period (DPP) of the system are 25.68% and 8.56 years.The price fluctuation of fuels and products has a great influence on the economic performance of the indirect coupling system.The environmental impact analysis indicates that the indirect coupling system can inhibit the propagation of NOx and reduce the environmental cost.