In the present study, a robust modified weakly compressible smoothed particle hydrodynamics (SPH) method is introduced in order to examine the micromixing phenomena within a cylindrical paddle mixer. Because it has a Lagrangian nature and it is based on particles, smoothed particle hydrodynamics is an appropriate and convenient method for simulating the moving boundary problems and tracking the particles in the mixing process. The present study thus introduces a convenient SPH method for modelling the mixing process. The straight and cross‐shaped blades are considered, and the effects of the fixed rotation, planetary motion of the blade, and position of the blade on the mixing rate are studied.