Solid mixing dynamics is of vital important to the processing rate, achievable homogeneity and product quality in the related industries of paper, solid mixing behaviors within a baffle-type internally circulating fluidized (ICFB) are numerically investigated using a three-dimensional computational fluid dynamics-discrete element method (CFD-DEM), in which the gas motion is modeled by means of large eddy simulation (LES) while the solid kinematics is handled by a soft-sphere model. On the basis of the simulation results, typical snapshots of granular mixing dynamics in the bed are mixing index, is evaluated. Meanwhile, the solid circulation pattern is illustrated by tracking tracer positions both in the three-different parameters, such as sampling grid dimension, bed aeration setup, diameter and density of the solid, and the gap height beneath the baffle, on the mixing behaviors are also investigated. The results show that macroscopic circulation of solid plays a dominate role in the mixing process of the bed. Judgind by the tracer trajectory with time, a better transverse mixing can be obtained, and the mixing mechanisms are further analyzed. Besides, it is found that mixing rate and degree are insensitive to the sampling grid size and a nice mixing level can be obtained within seconds providing enough aeration to the bed and a proper gap height. Meanwhile, lighter and smaller particles possess better mixing ability, as they are easier to fluidize. Furthermore, this ICFB exhibits additional potentials in solid mixing compared with the corresponding fluidized bed.