Abstract: The gas-solid flow structure in FCC riser was studied in detail in a CFB cold model unit using ring-feeders with different form. Based on the gas and solids distributions, relative gas-solid contact efficiency (RCE) and cross-sectional gas-solid contact efficiency (CCE) were calculated and compared. Experimental results indicate that solid concentration and gas-solid contact efficiency could be different in riser with different form of feeder. However, the effect of the feeder form on the gas-solid flow structure is diminished along with the increase of riser height.