Abstract: By means of a cold state device of dual fluidized bed,the effects of fluidization air and loose air on the fluidization form of particles in the fluidized bed,the height of the granule and the amount of solid circulation are investigated. When the fluidization air is5 m~3/h,the particles in the fluidized bed gasifier are bubbling. The height of the granule is related to the pressure difference on both sides of the feed recycle devices. The greater the pressure difference,the lower the height of the granule in feed recycle devices. The pressure difference between the two sides of the feed recycle devices becomes smaller when the gas is reversed,and the height of the granule gradually increases. Without changing other conditions,when the lower loosening air is 3 m~3/h and below,increase the loosening air,and the particle circulation volume gradually increases. For this set of devices,the solid particle circulation volume reaches a maximum of 6.72 kg/h under certain conditions. The numerical simulation of the device shows that the fluidization form of particles in the model is consistent with the experiment.