Abstract: When the desulfurization in circulating luidized bed( CFB) boiler can not meet the discharge requirements,further purification of exhaust gas is needed. There are two options for the exhaust flue gas desulphurization( FGD) in the circulating fluidized bed boiler,such as limestone-gypsum wet FGD and CFB semi-dry FGD. In order to identify the most economical and suitable FGD technology for circulating fluidized bed combustion conditions,the techno-economic analysis model was suggested and the techno-economic index for two processes was predicted under the condition of full load and 70% desulphurization efficiency in the CFB combustion by limestone injection. The model results indicate that the operating cost and total cost of CFB semi-dry FGD technology are relatively low,require sulfur contents is required below 1.1% and 2.1%. The cost proportion of the desulfurizing agent for( CFB) semi-dry FGD is significantly large,while the electricity cost proportion of limestone-gypsum wet FGD is slightly large. Limestone price,on-grid power tariff and annual operation time are the main factors affecting desulfurization cost. The sensitivity of limestone to desulfurization cost is greater than that of on-grid power tariff.On the basis of the furnace desulfurization efficiency of 70%,the operating cost of limestone-gypsum wet FGD is higher than that of CFB semi-dry FGD when the price of limestone is less than 112 yuan per ton. When the on-grid power tariff is lower than 0.43 yuan per kilowatt hour,the operating cost of limestone-gypsum wet FGD is relatively low. The total cost of CFB semi-dry FGD is lower than that of limestone-gypsum wet FGD within the fluctuation range of limestone price,electricity price,and annual operating time. Compared with the conventional furnace desulfurization technology,the desulfurization cost of the ultra-fine limestone furnace desulfurization technology is lower,and the comprehensive advantages combined with the CFB semi-dry FGD technology are more prominent.