Abstract: Fine coal (3 -1 mm) is between pulverized coal and particles that is suitable for traditional air dense medium fluidized bed. The addition of fine coal can thus affect bed fluidization and separation characteristics. To elucidate the bubble-driven mechanism,the fluidization characteristics,pressure fluctuation,separation / mixing ef- ficiency of fine coal and fluidized bed density at different heights were investigated by varying number in an air dense medium fluidized bed using high-speed dynamic camera. Results show that bed density decreases while flu- idization quality changed slightly with the addition of fine coal. With the increase of gas velocity, coal particles separate initially,then change into mixed state. Meanwhile,bed density changes at different heights. When fluid- ization number is in the range of 1. 8 to 2. 0,coal particles achieve a maximum separation efficiency. However, with the gas velocity further increases,the influence of air flow increases,and coal particles could not be separated according to fluidized bed density strictly.