This paper presents a hybrid optimization method aiming to design the flow channel shape and reduce its flow resistance or pressure drop. The method combines flow pattern construction-based optimization with natural heuristic optimization. Firstly, an optimal flow field with minimum viscous dissipation is constructed. Then the channel shape is adapted by substituting the fluid cells that have lower dynamic pressure in the optimal flow field with solid cells. With solid cells being inserted into the flow domain, the channel volume decreases. This process (i.e. constructing optimal flow field and inserting solid cells to the flow domain) is repeated until the channel volume decreases to a certain value. As an intermediate result, a preliminary optimal channel shape is obtained. The second step of the hybrid optimization method is to further optimize the preliminary shape using the natural heuristic optimization. That is, the positions of the solid cells and fluid cells are exchanged stepwise. Ultimately, a streamlined channel shape is generated with reduced pressure drop. To demonstrate the validity of the method, a right-angle elbow, a straight tee channel and a multi-inlet channel are optimized, respectively. (C) 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.