The mixing transport courses of three-phase particle flows exist in some industrial applications, such as metallurgy material extraction, lithium electric slurry dispersion, and material mixing in the high-end chemical industry. Its mixing transport mechanism is a fluid−structure coupling dynamic issues with intensive shear and nonlinear characteristics, making the real-time prediction of the flow field face challenges. To address the above problem, a bidirectional fluid−structure coupling three-phase particle flow dynamic model is built based on the coupled computational fluid dynamics and discrete element model (CFD-DEM) to explore the mixing transport mechanism. An interphase coupling solution method is utilized to solve the interaction effects of the fluid and particle. Research results illustrate that the proposed method modeling can well reveal the mixing transport mechanism of the three-phase particle flows. Due to the additive effects of stirring speed, stirring blade size, and stirring blade structure, the flow field near the blade has a high-velocity gradient change, while the flow field away from the stirring blade has no significant change. When the particle material settles and accumulates to a certain extent, the particle movement is blocked, and the stirring speed of the particle material near the blade is reduced. The mixing effect of the particle material will be reduced near the wall. It can provide a valuable reference for particle flow transport and pattern identification and support technical support for lithium electric homogenate mixing, chemical extraction, and pharmacy process regulation.