Abstract: In a 0.5 meter diameter semicircular jetting fluidized bed with 42mm diameter semicircular nozzle,the transition of flow regime and the penetration depth were investigated.The penetration depth was recorded by a National M-7 video camera and analyzed frame to frame on a Panasonic HD-100 player.There were two flow patterns of jet and spout in a large jetting fluidized bed with increasing jet gas velocity.Spout appeared when jet gas velocity was high and static bed height was relatively low.The results from processing the signals of pressure fluctuation by multistage power spectrum analysis showed that the major frequency of pressure fluctuation increased with jetting gas velocity.On the basis of the experimental data,an equation describing flow regime transition was presented.Meanwhile,experimental data showed that penetration depth increased with increasing of jetting gas velocity.A correlation to calculate penetration depth was also proposed.