A large scale cold model experimental setup for a coupled reactor mainly composed of lower riser and upper gas-solid loop fluidized bed was established，aiming at the industrial application background of olefin reduction technology with auxiliary reactor for FCC naphtha upgrading.The hydrodynamic behavior in the upper loop fluidized bed was experimentally investigated.The results show that，under the coupling operation of loop fluidized bed and riser，two kinds of circulating driving forces exist in the loop fluidized bed viz.the static pressure difference and the particle jet driving force.The total averaged solid holdup difference between the draft tube and the annulus region increases with increasing superficial gas velocity in the draft tube，but decreases with increasing external particle circulating flux.Particle circulating velocity increases with increasing superficial gas velocity in the draft tube and external particle circulating flux.Furthermore，a flow mathematical model describing the coupling operation of riser and loop fluidized bed was established on the basis of momentum balance principle of loop fluidized bed，and the model average relative errors were within 15.95%.