Abstract: In a Ф0.5m×8m semicircular jetting fluidized bed with double nozzles using millet as fluidized material, studies of various flow regimes, i.e.,separate jet regime, transition flow regime and jet coalescence regime were carried out.The equations of transition of flow regimes were proposed.Experimental results indicated that penetration depth increased with increasing jet gas velocity,while penetration depth decreased with decreasing nozzle pitch.A relationship of penetration depth and nozzle distance in a large jetting fluidized bed with double nozzles was obtained.With smaller nozzle distance, jet coalescence always occurred and jet coalescence height replaced the penetration depth.Thus,a correlation of jet coalescence height was also presented.Meanwhile, deterministic chaos theory was used to investigate the flow hydrodynamic characteristics in the bed.When p/d 0 is equal to 5.48,the curve of correlation dimension vs .jetting gas velocity showed a maximum increase rate corresponding with complex flow structure.Correlation dimension increased with static bed height.