Abstract: Through dynamic characteristic analysis on the structure and in-furnace temperature of a circulating fluidized bed boiler (CFBB) , balance equations were set up respectively for oxygen volume fraction, bed material flow, carbon residue and dynamic energy in the furnace, cyclone separator and external bed, following which dynamic models were established, by taking the coal feed rate, primary air flow, secondary air flow, slag discharge and fly ash flow as the input variables. Based on the field data of Sichuan Baima 300 MW CFBB, numerical simulations were carried out using Matlab software, during which dynamic response of bed temperature was obtained under step disturbance of primary air flow and coal supply. Results show that the simulation results agree well with the actual operation data and can better reflect the dynamic response of bed temperature under disturbance of input variables.