Abstract: To find the optimum operating conditions and design parameters for coal gasification of large-size pressurized fluidized bed, a number of simulation models were built up, including the solid particle model, gas-phase model, hydrodynamic model of bubbles and the enthalpy balance model, etc., based on which the effects of following factors on the carbon conversion rate, gas production rate and cold gas efficiency were analyzed, such as the coal feed rate, the oxygen mass and the steam flow, etc, and subsequently the optimum range of coal feed rate was determined. Results show that the carbon conversion rate is kept at a level higher than 99% in the initial stage, and for gasifiers with same bed area, their handling capacity may be increased by raising the operation pressure; the gas production rate per kilogram of coal will be increased by 34%, when the operation pressure is raised from 1.5 MPa to 2.1 MPa (raised by 40%); for an operation pressure of 2.1 MPa, the optimum range of coal feed rate is from 2.0 kg/(m2·s) to 2.5 kg/(m2·s); the cold gas efficiency may get up to 77% when the oxygen-coal ratio is in 0.6-0.7; the heating value of generated gas is in direct proportion to the steam-air ratio.