Abstract: The co-pyrolysis characteristics of straw and low rank bituminous coal were investigated in a self-designed fluidized bed pyrolysis device,and the influence of temperature,pressure and feed rate on dust removal efficiency on the pyrolysis oil yield was studied. The results show that: with the condition of biomass blending ratio of 70 ∶ 30,600 ℃,0.3 MPa and nitrogen atmosphere,straw pyrolysis can provide enough hydrogen and alkaline/alkaline earth metal elements to balance the reaction of free radical and hydrogen donor in coal pyrolysis,change the caking property of coal,destroy the caking coke reaction of coal,and release the volatiles to the greatest extent. The total yield of co-pyrolysis oil is 16.90%,which is 13.05% higher than the theoretical value. With the increase of temperature,the density,viscosity and other properties of dusty gas are changed,and then the movement law of dust is changed. The dust removal efficiency increases at first and then decreases,influenced by enhanced thermal agglomeration and increased viscous resistance of char particles. The maximum dust removal efficiency reaches 94.8% at 450-500 ℃. When the pressure of pyrolysis increases from 0.1 MPa to 0.7 MPa,the gas-solid separation efficiency decreases from 97.52% to 96.34%,and the yield of pyrolysis oil decreased from 21.05% to 18.64% due to inhibition of volatilization under pressurized condition. The gas-solid separation efficiency is reduced because of the high powder concentration with high feed rate. The feed rate increases from 1.0 kg/h to 2.5 kg/h,the gas-solid separation efficiency decreases from 98.2% to 93.5%,the yield of pyrolysis oil decreases from 21.05% to 18.22%,and the dust content in oil increases from 1.05% to 5.04%.