Abstract: Circulating fluidized bed（CFB） is used as the preferred equipment for the thermal utilization of low calorific value solid waste because of its wide range of fuel application. In order to solve the problem of difficult control of pollution caused by improper fuel ratio in circulating fluidized bed combustion of heavy mixed fuel, soft coal gangue（SCG） particles and refuse derived fuel（RDF） particles were used as heavy fuel in this paper. The flow, temperature and gas composition distribution of three different primary fuel ratios in the staged combustion process of circulating fluidized bed boiler were simulated by Euler two-flow model using staged combustion technology, so as to obtain the best primary fuel ratio for staged combustion in circulating fluidized bed. The results show that: The ratio of SCG/RDF of 5/2 can promote the collision frequency between particles and fluid and increase the pyrolysis reaction intensity of volatiles in HCG.Under this ratio, the reaction rate of volatiles in the dense phase region is 0.025 and 0.01 higher than that of SCG/RDF of 6/1 and 3/4, respectively. At the same time, the overall furnace temperature of this ratio is 175 K and 25 K higher than that of SCG/RDF at 6/1 and 3/4, respectively, which achieves the best effect of fuel co-combustion. The O₂consumption at this ratio is 0.08 and 0.01 higher than that of SCG/RDF at 6/1 and 3/4, respectively. In addition, the increase of RDF ratio will reduce the content of pollutants NO and SO₂. Therefore, when the ratio of SCG/RDF is 5/2, the optimal operation state of staged combustion of heavy fuel can be achieved, and the circulating fluidized bed combustion effect of heavy fuel is the best.