A numerical study on the flow field and particle mixing behavior in spouted beds with the aim of considering different base shapes was carried out using CFD-DEM modeling. Four spouted beds with different base angles of 180, 120, 90 and 60 degrees were compared. In order to have a qualitative and quantitative analysis on the mixing behavior, particle tracing and Lacey mixing index calculation were executed for the models. Rectangular spouted beds generate dead-zones in the corners of the system that causes less ultimate mixing index value. As the base angle decreases, the mixing index tends to increase. A mixing degree of the case with 180 degrees base angle reaches no more than 79% at the end of the simulation, which is the lowest, whereas a mixing degree of the 60 degrees base angle reaches the maximum value of 97%, which is the highest. Particle tracing conducted in these models indicates that this matter is due to the observed fact that with more incline of the base walls, particles slip more into the spout, thus entering the circulating flow. The results also indicate this increase in the slope has almost no effect on the rate which the mixing index reaches its maximum value.