A disc microreactor with constructal tree-shaped flow architecture is introduced for methanol steam reforming. For this design, a three-dimensional model is developed and analyzed numerically to predict the resulting hydrogen production. The methanol conversion ratio, yield of hydrogen production in the product of the tree-shaped microreactor, are all evaluated and compared with the corresponding microreactor using a parallel flow pattern. In addition, the effect of branching level, steam to methanol ratio (SMR), and inlet velocity on the reaction performance of the microreactor with a constructal tree-shaped network are also investigated and discussed. The results indicate that the methanol conversion in the disc tree-shaped microreactor is more than 10% better than that of a parallel microreactor. Furthermore, the yield of hydrogen at the outlet of the disc tree-shaped microreator is greater than the parallel flow configuration. The CO concentration in the products of the disc tree-shaped microreactor is higher than that of parallel microreactor. In addition, the disc tree-shaped microreactor with a larger branch level behaves enhanced performance on the methanol conversion and hydrogen production. (C) 2013 Elsevier Ltd. All rights reserved.