A two-stage dust removing system was designed by setting a finger roller in the exhaust cylinder of typical cyclone to improve the dedusting efficiency from flue gas of straw carbonization.The model of the system was established in SolidWorks and meshed with ANSYS ICEM.The flow field of the system was setup through simulation of the system with combination of RNG k-ε model and RSM model.The particle separation efficiency was simulated with DPM model coupled of gas-solid two phase flow based on the Euler- Lagrange equation.The static pressure,tangential velocity,radial velocity,axial velocity distribution and the separation efficiency of different size particles of typical cyclone and the 2-stage dust removal system were obtained at inlet velocity of 20 m/s and finger roller rotation speed of 0 r/min,900 r/min,1 450 r/min and 2 900 r/min.The results showed that the rotation speed of the finger roller had a significant effect on static pressure of the dust collector and the static pressure increased with the increase of rotation speed compared with typical cyclone.The rotation speed of the finger roller had a significant influence on tangential velocity of the flow field.The tangential velocity increases with increase of the rotation speed with little effect on the radial velocity and axial velocity.Compared with typical cyclone,the 2-stage dust removing system and its rotation speed had little influence on separation of dust particles of diameter less than 1 μm.However,they had significant effects on separating dust particles of diameter larger than 10 μm,and the separating efficiency increased with the increase of rotation speed of the roller.The difference of separation efficiency of different rotation speed was not significant.It will provide reference for designing and optimizing the structure of dust removal device with high efficiency.