The moving granular bed filter has been developed for high-temperature gas cleanup. The existence of stagnant zone is an important problem to be solved since the dust particulates and fly ash coming with flue gas may plug the system and the filtration efficiency decreases remarkably. We proposed the idea of placing sublouvers into the convergent channel between louvers. The idea has been demonstrated the possibility to diminish the stagnant zones. This paper tries to study the influence of vertical shift of the sublouver position on the flow pattern. A quasi two-dimensional cross-flow moving granular bed, with systems of louvers and sublouvers, was used as the experimental facility. We used the silica sands as filter granules discharged from an upper hopper and circulated to the bed. An image processing system was used to record the granular flow for analyzing the flow patterns and velocity fields of filter granules. In this study, the optimum design of louver-sublouver moving bed has been demonstrated to almost completely eliminate the stagnant zones. Besides the quasi two-dimensional cross-flow moving bed tests, we also tested a three-dimensional moving bed using the optimum design of louver-sublouver. The results were also very satisfactory. (C) 2008 The Society of Powder Technology Japan. Published by Elsevier BV and The Society of Powder Technology Japan. All rights reserved.