Semi-coke has the characteristics of low volatile matter and high fixed carbon. Compared with pulverized coal boiler, circulating fluidized bed (CFB) boiler is more suitable for semi-coke combustion. In order to understand the combustion performance of the circulating fluidized bed boiler for semi-coke, the one-dimensional circulating fluidized bed boiler model was used to simulate a CFB boiler for semi-coke. By comparing the model prediction of particle size distribution of circulating ash and bottom slag with the measurement results of field sampling, the two match well and verify the reasonableness and accuracy of the overall boiler model. Through simulation, the effects of cyclone efficiency and semi-coke particle size on semi-coke CFB boiler were analyzed. The simulation results show that the cyclone efficiency has a very significant impact on the performance of semi-coke fired circulating fluidized bed. Improving the cyclone efficiency can increase combustion efficiency of semi-coke, and median particle size of fly ash is recommended to be controlled around 10 μm.Feed coal particle size has an important effect on the CFB boiler of semi-coke. The combustion efficiency is decreased by reducing the semi-coke particle size, and NOx emission can be reduced significantly.According to the ash formation characteristics of semi-coke, the inject particle size should be in the range of 0.5-6.0 mm.Comparing with the circulating fluidized bed boiler burning lignite, the temperature in the furnace is higher when burns semi-coke, and the combustion efficiency is lower. Both SO2 emission and NOx emissions in the combustion process of semi-coke are low, but it still needs flue gas denitrification systems to meet the pollutant emissions. All above results provide a direction for the operation optimization of CFB boiler that fires semi-coke.