DEM was employed to numerically reproduce the mixing process and flow behavior of different systems of spheres and cylinders, where the effects of rotation speed, aspect ratio (AR) of the cylindrical particles and mass fraction of cylindrical particles to total particles (C/T) were systematically investigated. The motion behaviors and corresponding mechanisms in improving mixing performance have been also explored from the microscopic scale. The results show that the binary mixture with AR = 1.0 gets a higher mixing rate at 40 rpm when C/T = 0.6. As the rotation speed increases, the mixture reaches a higher position and the velocity difference between spheres and cylinders increases, which leads to the flow regime transformation and then promotes the mixing process. Interlocks between particles becomes weaker and pores can be effectively filled when AR ≈ 1.0, which result in higher packing density and facilitate the transfer of force and energy.