This paper concerns the velocity fields of three symmetric louver-walled moving-bed systems. The louver angles were 10 degrees, 20 degrees and 50 degrees in the three experimental tests. The particle-tracking method and image-processing technology were employed to measure the granule velocity fields in the louver sections. The horizontal and vertical velocity distributions extracted from the velocity fields at five levels of the louver section were plotted and discussed. The velocity profiles of filter granules are influenced by the louver geometry. In the steeper louver-angle system, the velocity profile of filter granules is similar to plug flow. The stagnant zones exist along the louver walls in the filter system with shallow louver sections.