Abstract: To increase particle concentration and reinforce internal circulation in circulating fluidized bed-flue gas desulfurizer(CFB-FGD),an internally circulating and multistage spouted tower was presented and an experimental installation was established.By changing inlet gas velocity，particle concentration and distance from tower-top, the particle concentration and resistance force were predicted by using the collapse bed method.An internal concentration scale was obtained.A numerical study was conducted to simulate particle flow.Predicted particle concentration,resistance force and other parameters agreed with experimental data.The conclusions are good reference for engineering application.