In order to develop the prereduction fluidized bed for smelting reduction process, the fluidization and reduction characteristics of iron ore fines with a wide size distribution, such as sinter feed, were examined. As a result, if the superficial gas velocity is kept over than 2 or 4 times of minimum fluidizing velocity, the segregation of coarse particles can be avoided, and it became clear that the appropriate mean residence time to produce prereduced iron ore of about 20-25% reduction degree was from 30 to 60 minutes. On the basis of these results, a hot model of fluidized bed were so designed that the residence time of fine particles could be controlled by the circulating device, and the characteristics of this hot model were experimentally confirmed. Then, the simulation model considering the elutriation rate of fine particles was made to estimate the operating condition. Furthermore, with the analysis by two-phase model, it was found that the gas interchange coefficient has little influence on reduction behavior, and the fundamental design of the distributor for prereduction fluidized bed was investigated.