The structural theory of thermoeconomics was applied to a 75 t/h coal combustion circle fluidized boiler polygeneration system. Four energy products including steam, electricity, fuelgas and tar were analyzed by the modeling on both unit exergy cost and thermoeconomic cost of all yields. Given the designed operating condition of the polygeneration system, some conclusions were deduced through above methods. Among the total energy products, the steam yield is most influenced by the price fluctuation of coal fuel. When the gasifier is operating at the range of 600 ℃ to 800 ℃, all yields from the polyenergy generation system are decreased with the elevation of running temperature of gasifier. The unit thermoeconomic cost of steam produced from the polygeneration system is 16.35% less than that yielded from the combined heat and power system, but as for the electricity generation, the cost rose from the polygeneration system is 20.57% less than that from the combined heat and power system. Such results show that the structural theory of thermoeconomics is a prospective tool for economical analysis on the power generation system and a potential reference for the optimal design and malfunction diagnosis.