We designed and fabricated a microreactor with paralleled packed beds suitable for the direct synthesis of hydrogen peroxide from hydrogen and oxygen. The reactor is based on microfluidic design for equal distribution of reaction fluids to each catalyst packed bed, which was validated by the reactor performance and gas- and liquid flow regime visualization. We extended the concept to parallel operation so that 1 kg/day of 4 wt% of hydrogen peroxide was produced by 4-reactor parallel operation. Our strategy gives an alternative opportunity to the scaling-up strategy of flow chemical process technology, by overcoming the fluid maldistribution problem in a gas-liquid and solid multiphase system. (C) 2014 Elsevier B.V. All rights reserved.