Particle transport in microchannel is presented. This article focuses on situations in which the sizes of the particles are comparable to the sizes of the channels. These solid bodies are sufficiently large that momentum is exchanged between the bodies and the flowing fluid. As a result, the solid bodies affect the fluid flow significantly, and vice versa, resulting in a transient process in which the motions of the solid bodies and the flow field are strongly coupled. The flow field and the particulate flow must then be solved simultaneously. The solid bodies are modeled as a fluid constraint to move with rigid body motion. The solid-fluid interface is described using a distance function. For demonstration purposes, the finite-volume method is used to solve the resulting set of governing equations. The present approach is validated against (1) flow around stationary, (2) flow around forced rotating, (3) flow around freely rotating cylinders, and (4) sedimentation of a circular cylinder under gravity. Finally, the motion of particles carried by an incompressible fluid in a microchannel system is studied.