In this study digital holographic microscopy system for measurements of 3-D velocities of particles in MR fluid is devel-oped. Holograms are recorded using either a CCD camera with a double pulse laser or a high-speed camera with a contin-uous laser. To process recorded holograms, the correlation coefficient method is used for focal plane determination of particles. To remove noise and improve the quality of holograms and reconstructed images, a Wiener filter is adopted. The two-threshold and image segmentation methods are used for binary image transformation. For particle pairing, the match probability method is adopted. The developed system will be applied to measurements of the characteristics of unsteady 3-D particle velocities in MR fluids through the next stage of this study.