Abstract: Computational simulation is a widely adopted method to study the spouted bed, or other industrial facilities. With the simulation problems becoming more and more complex, for example, higher solid particle numbers and higher demand to better describe the collisions between the particles, many researchers have contracted the third dimension of the bed in their simulation to ease the computational burden. In the present work, the gas–solid flow in a 3-D and quasi 3-D slot-rectangular spouted bed with same geometry parameters except the depth is numerically investigated with CFD-DEM to explore the depth effect on the hydrodynamics of the bed. The results demonstrate that: With bed depth increasing, the minimum spouting velocity and maximum pressure drop decreases initially and then remains a constant value. In the quasi 3-D bed, the flow pattern of steady spouting regime occurred in 3-D bed cannot form although a high superficial velocity is given, and the incoherent spouting state may cause the highest bed layer thickness to be twice that of the normal operation. In the spout region, the higher gas voidage in 3-D bed shows a larger spouting diameter than quasi 3-D bed. The time averaged flow rate in the spouting and motionless region of the quasi 3-D are obviously higher than that of the 3-D case.