The objective of this work is to study the influence of complex manifold geometries on the flow distribution between microchannels by an analytical model and an equivalent electrical resistance network model. An optimization procedure is proposed to optimize the manifold geometries and dimensional variations to obtain comparatively ideal flow distribution between microchannels. A specific case is illustrated by applying the proposed optimization procedure to analyze the optimal rules for a given inlet distributing manifold geometry. Result shows that the microchannel width dominates the optimization of outlet collecting manifold geometry and dimensional variations. (c) 2007 Elsevier B.V. All rights reserved.